It's wild how overpriced Tesla Powerwalls are.
16 kWh battery with all of the UL supported listings etc = $3300 [0]
13.5 kWh Tesla Powerwall is $12k~$15k
You would get your return way back quicker.
[0] - https://www.ruixubattery.com/product-page/lithi2-16-battery-...
EDIT: As others have pointed out, powerwalls have inverters built in so it's not totally apples to apples. You can get a beefy inverter for $5k and it's still cheaper and you wouldn't need an additional inverter every time you add a battery.
Battery prices are getting really low, if you're willing to do some DIY. Just received a 15kWh battery from China. A 'Humsienk'. Combined it with a GroWatt SPA3000TL-BL inverter.
Total price, 1600 euros. So close to the magical 100 euros per kWh. Driving it with some interesting combinations of Raspberry PI's and serial interfaces and custom written Go code, but it works... :)
Did the same, got a solar installer to fit panels on garage and a solis hybrid inverter. They fitted a CT clamp on my meter and a lora device on both sides for it to communicate with the inverter.
Then bought a 16kwh battery for ~£1500, installation was plugging in a positive, negative and ethernet cable and configuring the inverter to use the battery. (if my home insnurer is reading this, I had an electrician friend double check while helping with some other work)
Definitely recommended for anyone who likes tinkering, thousands cheaper than installer pricing.
> Battery prices are getting really low, if you're willing to do some DIY.
Willing and allowed. In some countries it can only be done by certified electricians.
UK considerations: must be at least signed off by an approved electrician ("Part P" regulations), and for any situations involving subsidy needs to be MCS approved as well. https://mcscertified.com/
Find an electrician who will inspect and sign off on your work. It's not illegal as licensed master electricians have mechanics do all the grunt work who are unlicensed. The electrician vouches for his employees work which legitimizes it. No different than you doing the work and having the electrician inspect, call out issues to fix, and inspect again until no issues are found and sign off.
Surely it only needs to be signed off if you intend to sell the property with them or sell excess back to the grid. If youre just using the batteries how is anyone going to know?
I'd assume your fire insurance covers nothing if illegally installed batteries are found inside after a house fire.
If the DIY work wasn't the cause for the fire it shouldn't matter, but I half-expect someone to inform me that US insurance companies can (legally) deny coverage for reasons unrelated to the accident.
If is something does happen, and Li Batteries catching fire is not something unheard of, you will be in a world of suffering. Probably having no home, and having to pay damages to the neighbors. All to save what? 2k$... 5k$?
I paid an electrician one hours work to actually connect my inverter to my main 200A panel, and he even got the required building permit required.
Then pay one to inspect it and sign off for you.
Theoretically a good choice, but where I live, just doesn't work. Either they just say "no thanks" or they will be more expensive than letting them do the whole job.
I got the "trick" recommended to do the things yourself, then call a certified guy, and say "look, I contracted a guy, I had no idea, he came did everything, but I got a bad vibe, I would like you check the whole installation". But it also does not really work, they will come with a contract, where you are enforced to contract them to correct any findings. And boy they will find things then...
It varies for sure but in my case it helps to know people.
I mean, it "can" be done without a certificate.
It "may" not be permitted, but if you live in a collection of shacks in rural Colorado that were themselves -already- completely un-permitted then you might decide that it's best to just do the work yourself.
We are finally starting to see Chinese prices externally.
It’s been crazy seeing the western home storage market selling systems with the €/kWh being more expensive than buying a BEV. And that includes a car.
https://www.docanpower.com/eu-stock/zz-48kwh-50kwh-51-2v-942...
I do wish I could have a good, in-depth tutorial on how to set this up myself. Along with (pipe dream) an explanation of how it would interact with my local utility. I worry that due to some silly technicality, I won't be able to export to my local utility, or else I won't be able to run off-grid when there's an outage.
I will do a write-up in a couple of days. It's all relatively simple, you just have to expect terrible documentation and do a bit of reverse engineering and serial sniffing. I expected the battery to be complicated, but it turned out that the inverter was.
You'll encounter stuff like: manual says use RS485 port on Battery for GroWatt inverter → need to use CAN port on Battery. Meter Port (RS485 [serial] over RJ45) wiring on GroWatt is unknown (A: white orange / B: white blue, cross them over). Dinky RS485 serial → USB converter needs a 120ohm resistor between pins for line termination. Growatt meter port expects a SDM630 meter, not a DTSU666 (hardcoded), so vibe code another emulator. DIP switches for RS232 connection need to be both on the ON position (undocumented). CH340 USB→serial converter for RS232 does not work, but one with a Prolific chip does. Etc. etc. etc :)
Oh, and the biggest one... I was expecting to be able to just send a command, 'charge at 500watts', now... 'discharge at 2000watts'. But no. You have to emulate a power meter and the inverter will try to bring the net power to 0. Fun! :)
I would appreciate this write up as well. Looking to do a DIY setup.
> Driving it with some interesting combinations of Raspberry PI's and serial interfaces and custom written Go code, but it works... :)
What protocol is it speaking? I've seen some of the more mainstream models call out that they use Modbus but all the cheap import models either might use Modbus or some custom protocol you have to reverse engineer or hope someone else did.
Yup, Growatt is the Chinese OEM that Base Power white labels to pretend it does US manufacturing. In fact this stuff is low quality. You need to be careful. There are gradations of quality at cell, pack, inverter, control levels. You will be crushed if you realize you AliExpressed your way to a home power "solution" only to have it fail young.
Awesome.
Feel you have more unknowns on the safety front? vs. the expensive off-the-shelf. [in the USA, it’d also be “fewer names to sue” in that unlikely tragedy of combustion in home, but no euro/kWh targets there]
LFP batteries are as likely to burn down your house as a stack of wood is. I'd be worried about the inverter or botched DIY wiring (especially not to spec torque on terminal connections and botched crimps leading to hot spots), but not about the batteries themselves. For a person who wants to save some money, but doesn't know how to work with electricity, the best move is probably to get cheap LFP cells from China, but have a professional install a BMS and the remainder of the solar system.
> especially not to spec torque on terminal connections and botched crimps leading to hot spots
This was indeed my greatest concern. However the battery came with pre-crimped very solid DC wires, and nice push connectors for the battery itself. The battery also has an integrated DC breaker (great!).
The system runs 3KW max, so I just added an additional breaker (with RCD integrated) in the conduit box. In NL this is something a DIY-home owner easily can do themselves :) (just use the right solid/flex stranded cabling for the connectors, etc...)
And further, my position has been that learning the correct methods, paying a lot of attention to details, and not being cheap with tools is -still- cheaper and probably more reliable than paying contractors. I have only used my hydraulic crimper for a pair of cables, but it was the correct tool and did good work.
I'm not interfacing with a grid, and there are already code issues with my places- I'd probably feel different if I could get insurance on my place.
Cheap chinese tooling and youtube (plus pretty good general literacy) go a long way in this world.
And FWIW, I live in the US west and am way more worried about fire coming from outside than from the batteries.
> LFP batteries are as likely to burn down your house as a stack of wood is.
LFP batteries are much safer than past chemistries, but this statement is way too broad.
High power batteries are always more dangerous than something like a stack of wood, because batteries will gladly dump their entire energy capacity very rapidly into a short.
Even if the battery itself [mostly] won't self-immolate, the entire installation can be a fire hazard.
Treat them with proper respect.
> botched crimps
On a tangent, I’m amazed at how bad most random crimps I see on the internet are. Also, the number of people who debate the use of solder on crimps without discussing potential issues with said solder is too high.
9-11 year payback isn't bad based on the projections. You could probably goose it a bit with inflation of electrical prices (depends on how the electrical policies change and what they pass through).
I'll also add theres some O&M coming down the line. Inverters @ year 10, small maintenance and Im assuming you re-did your roof before you installed. Anyone putting solar up make sure you do it at the same time as a roof because taking it down to redo a roof kills your economic value.
> I'm assuming you re-did your roof before you installed
In the UK I would expect the roof to be tile, which lasts basically forever unless a storm hits hard enough.
I did have to have my panels taken down and refitted, at a cost of well over £1000, because I hadn't bird-proofed underneath them (wasn't suggested by original installer). So watch out for that one.
Yeah I need to un pigeon the underneath of mine.
How do you bird-proof them?
Fitting blocks (basically shaped plastic) around the edge to prevent birds from getting underneath and nesting. Merely landing on the panels isn't a huge nuisance, but nesting is.
It is essentially a bond return, with the caveat being that solar PV panels will last 25+ years with some degradation and reduction in output. To your point, the best arrangement (imho) is a standing seam metal roof (40-70 year lifetime) with the panels mounted via friction racking with no roof deck penetrations. This avoids the economic cost of pulling everything off the roof to re-roof, and should outlive any homeowner 40 years of age or older. I also expect labor willing to get on a roof becoming more scarce and expensive over time in the developed world, which I think should be taken into account. Your battery storage can be replaced 10-15 years from now at the end of its service life by anyone with a hand truck.
> essentially a bond return
You reminded me: David Roberts' often states that a hurdle for electrification and decarbonization projects is connecting them to "slow capital". Stuff like residential, community, solar, battery, heat pumps, appliances, ground source heat, yadda yadda.
I gather that there's plenty of "slow capital" perfectly happy with low risk long term modest returns. But these projects are too small to be worth the effort. Probably something about transaction costs.
My impression is there's an opportunity to bundle up these projects for the larger/largest investors. Biden's IRA created a "green bank" (RIP); maybe that was its intended function.
You're smart about money and finance, so you can probably explain what Roberts is talking about (to noobs like me).
Stay tuned, I have an idea to soak up global capital for these projects.
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This is factually inaccurate. Solar PV panels will continue to produce power at 80-90% of rated output after 25 years, and battery storage will still have 80-90% capacity. I'm sure you can understand that as long as the system is storing and producing power at these levels, its value is not zero.
https://magnifina.com/articles/rooftop-solar-yield/ explains it better than me attempting to write a wall of text.
> while the initial principal of your bond investment will remain intact.
As long as the bond issuer remains solvent. How much do you trust bonds that yield 9% to retain their full value for 25 years?
From the article:
"Another way to look at this is that the investment is returning ~9%/year."
Almost all simulations I've done across 3 countries with 3 different payback models for selling back to grid (one of the three doesn’t allow selling back almost anything above your consumption), I could never make investing in Solar not being a gamble.
You really need to gamble on odds of replacing equipment being very low for it to make sense. And in practice most people I anecdotally know that run it, after 5-7 years have already done additional purchases. The payback time keeps getting pushed back to the point that when payback will happen your panel will be worthless in efficiency compared to new ones. At industrial / commercial scale it makes sense, but humans like to move houses, and do stuff in the houses and that messes with the payback plans at the individual level.
So either I was in the wrong countries or most people just gamble on the equipment lifetime, but for that I'd rather buy SPY calls, less drama.
Having power when your entire neighborhood is off, priceless.
[edit: yes, I assume you also get batteries, I know that solar alone doesn't magically power your house.]
Outside transfer switch and a 10-20kw portable generator is like $4-5k. It requires manual switching but it works for us in our hurricane-prone region. Helped with last years 1 in a 100 year winter storm in our southern region.
Battery/solar doesn’t make sense in my opinion. Too many years to break even like this parent comment said and by the time you break even at 10 years, your system either is too inefficient or needs replacing. At least with the portable generator, you can move it with you to a new home and use it for other things like camping or RVing.
Context: I’m in the Netherlands. With taxes, power is around 25cent/kWh for me. For reference: Amsterdam is around a latitude of 52N, which is north enough that it only hits Alaska, not the US mainland.
I installed 2800Wp solar for about €2800 ($3000, payback in: 4-5 years), and a 5kWh battery for €1200 ($1300) all in. The battery has an expected payback time of just over 5 years, and I have some backup power if I need it.
I’m pretty sure about the battery payback, because I have a few years of per second consumption data in clickhouse and (very conservatively) simulated the battery. A few years ago any business case on storage was completely impossible, and now suddenly we’re here.
I could totally see this happen for the US as prices improve further, even if it’s not feasible today.
Is it priceless? I literally wouldn't pay more than $200 to have electricity for a day while the whole neighborhood doesn't. Anything more and I'd prefer to just keep the money in my pocket to be honest.
In my country I've never had to deal with more than 15 minutes, twice in my life. In other countries its sometimes been a day but really I just go on with my life.
Whats funny about that -- is you assume thats the case - but a lot of solar isn't installed to be backup power. With Storage yes, but straight up solar -> no.
It's not the default but you can get it installed that way or get it adapted later (less than ideal if you end up having to replace the inverter).
Yea, that costs extra. My dad went for the natural gas generator.
Well there are other, far cheaper ways to get that.
99% of systems are grid tie, so unless you’re spending another $7k for an ATS and associated infrastructure or you’re 100% off grid, your power still goes off.
And I should clarify that you technically can get away with a less expensive interlock system, but you're still paying a few thousand dollars to have your panel replaced (unless you feel comfortable doing that sort of electrical work yourself).
Making a system non-grid-tie is comparatively expensive, that's why grid tie is so common. People think you add solar + batteries and you're ready for doomsday - not quite.
im a systems engineer and cost analyst who has put together some modeling myself as well. as a personal investment on your house, i agree. The economic value of solar seems to be best applied as neighborhood or block purchases, like as part of a co-op or hoa. they would need dedicated infrastructure like a communal parking lot with solar overhead, or running them on the property line borders with an easement underneath for servicing, using property fencing as main support (with upgraded fencing)
basically, the way it really makes sense (to me) is to integrate it as part of a micro-grid system, possibly with generator backups and everything to also keep the lights on in the entire neighborhood if the main grid goes down.
its a higher upfront cost on paper, but way less variables with the roof and you are grouping multiple peoples needs together so the gamble goes down on repairs. the poles for ground-mounting can be used for 40 - 60 years, so you would get multiple panels out of them
probably a bureaucratic nightmare though
This is also true of heating and cooling, and I've never understood why we (in the US) build relatively dense housing communities but don't implement things like this. Having a separate air conditioner for each home, especially in a condominium/townhouse complex, has never made sense to me as it's so inefficient compared to central heating/cooling.
Having done 2 solar installs, one over 10 years and one 6 years, both going strong. Nothing else needed, it just sits there and produces.
So, from my experience, that's not the case. Maybe the people you know keep tweaking because they're enthusiasts like you have with cars.
It could be as simple as a different model. In one of those it was easy to make it feasible if you had no cap on how much to sell back, but it was limited to consumption plus like 10% or something like that. Since the property used very little energy but had a big roof we thought itd be a good thing to produce green energy while making a little money or even just breaking even, but to break even we'd have to use way more energy which was completely against the original objective. So its not like the technology isn't able to do it but the rules can make it very hard and a few years less of operation for some components make the math very difficult if you're conservative and want to ensure break even within some reasonable timeline
Too little capacity and it takes 50 years to absorb the fixed costs.
The payback math almost certainly improves if electricity prices keep rising faster than inflation
Wont you need to replace the batteries around Year 10 and then this becomes a wash?
Why would you need to replace the batteries? Do they fail outright at around 10 years, become unsafe, or do they just lose capacity?
Curious!
Even if they're at 50% capacity, they would still work, right? But if there are other considerations, especially safety ones, then that would definitely be a consideration. I'm not sure where to learn about this type of thing.
> Do they fail outright at around 10 years, become unsafe, or do they just lose capacity?
LiFePO4 generally degrades to 80% capacity after 10 years, that's it. Safety isn't an issue.
At which point if you're short on capacity (but who knows how your demand might shift over a decade) it's not like you need to replace the original batteries to get that 20% back, you will probably be able to just expand the pack to bring the capacity up.
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Rather like the car, think of panels as buying 20+ years of electricity upfront rather than being exposed to market rates. You can buy a car upfront, on credit, lease it, or rent it; in all of those the longer you commit the cheaper it is.
Not for everyone, but definitely for homeowners with suitable roofs and local utilities.
https://electrek.co/2026/01/06/catl-ev-batteries-significant...
> For example, CATL is one of four LFP battery suppliers at the Zhangbei National Wind-Solar-Storage Demonstration Project in China. CATL’s batteries are the only ones that have never been replaced, retaining over 90% of residual capacity after 14 years.
Batteries are not only not worthless after almost 15 years in service, they still have sufficient capacity to continue to operate. If you need that capacity back lost to degradation, add a battery ~15 years from now, they will only continue to get cheaper.
> Large solar farms and neighbourhood batteries operate at a much higher efficiency than domestic installations.
Maybe, but that power is typically generated far from where it's consumed and so you have significant transmission losses.
Is an ETF simple?
I get your point that in modern society, you can invest in an ETF in a few clicks, but in a way, owning your own infrastructure is simpler. Transform the sun into energy reserves with parts you can buy, understand, and install yourself from wholesalers.
A power company is opaque, carries overhead, and requires complexity to serve at an institutional level. ETFs have a similar complexity/abstraction to their customers.
I'm with you. I have no interest in owning, running, and maintaining my own personal electrical utility.
I'm happy to pay monthly to let my electrical provider handle all that, and I'll invest my money in something with a better return.
battery life span is defined as when the reach 80% of their original capacity. it's possible that the decline will accelerate after that point but they aren't suddenly useless
Presumably an exponential decay, as for most tool lifetimes.
Good analysis. And kudos to the author for saving money. But still 21.6MWh per year excluding solar production seems too high for a household. I use electric heating and drive an electric vehicle, and my household annual energy consumption is about one fifth of that.
Their total household usage was actually ~17.3 MWh depending on what data source you're using for their usage.
Given 6 MWh of exports with only 3.2 MWh of total solar production, they are cycling their powerwall to get paid for the fact that their off-peak rate is half the price of their peak export tariff rate which is inflating the number you're looking at.
That is still an enormous amount of electricity for a single family to consume.
Sorta, kinda, it depends.
In my house I only run LED lighting and an occasional oven, some phones and laptops, a cycling fridge and two weekly wash cycles, in other words, virtually no electricity. I'm at like 2 kWh per day.
The ~45 kWh a day for this family is gigantic compared to mine, like >20 of my homes in one.
But I don't have an electric car, nor electric heating or cooling, nor an electric stove.
If you have say a standard electric car like a Peugeot 208 which uses 15 kWh per 100km, and you both drive one hour (say 60km) to work and back, five days a week, that's already 25 kWh per day.
My heating bill (gas, europe) is an order of magnitude of my electric bill. Even if I'd electrify it (cheaper), it'd likely be an additional 10 kWh per day.
If you have slightly more fancy lifestyle (they run home-servers and a hottub for example), you can easily get to 45 kWh.
I think the fair comparison is to look at a household total energy expenditure (energy & $). My household has a low electrical share, theirs has an almost exclusive electrical share.
I ran my power bill for a small single family home through chatGPT and it was interesting. Cold winters/hot summers, electric stove, air conditioning during summers, and nothing else out of the ordinary that uses power.
- Base electricity: 17 kWh/day (10 in months without AC)
- Heating (currently gas): 33 kWh/day
- Heating (if I switched to heat pump with COP 3): 10 kWh/day
- EV charging at 10k miles/yr: 9 kWh/day
Total if I was fully electrified: 36 kWh/day, or 13 MWh/yr
He mentions that he has a server. It wouldn't surprise me if that consumes the majority of that.
I had a old, cheap, used Dell R710 that I bought used in ~2016 until 2025. It only took a few months of running a new, much more efficient server to pay for its self.
It's less than 50kwh a day, high but seems reasonable with 2 electric cars.
Not all homes are made equal: different appliances & electronics from different vintages, etc.
I have 2 EVs (Tesla and BMW), an electric oven, and a homelab rack (but no HVAC), and my usage was 34.4 MWh last year — with 100% from Solar and Powerwall.
That’s an awful lot of power.
I’m waiting on a quote for an hvac that uses its waste heat for the home hot water. Im irritated that I’m cooling the house, pushing out hot air, and heating water at the same time.
Get a basic heat recovery unit, it basically has no moving parts (just a few fans) and good ones recover 90%+ of the heat going out of your house. It's almost useless if you don't have an airtight envelope though.
All in one systems with water heating are way too complex and _will_ fail relatively quickly, mini heat pumps won't last 10 years, and by the time it dies you won't be able to find a replacement for your specific model
> Can you offer some evidence of this? I don't see how adding a refrigerant to water heat exchanger after the compressor, before the reversing valve, could possibly hurt the longevity of a system.
The nearly infinite amount of forum posts about heat pumps dying prematurely and costing thousands and thousands to fix. You don't see how adding complexity on top of complexity in a complex system add points of failures ?
> Thing with mini-splits is you replace the entire unit so it doesn't matter.
I forgot this is an american centric forum and things are just made cheap/disposable because "it's cheaper'
This makes me sad. I’m in a 1940s house where the lack of it being airtight is a key reason it’s still standing as it leaks and the airflow dries it. Water flows down the inside of the brickwork, and the cavity is well ventilated.
Yay for New Zealand housing.
On that avenue, I do push hot air from my homelab into my upper garage for heat. If it below 50deg outside I also bring in some cold air from outside. Both are somewhat free offsets for heating/cooling.
You just need an air source heat pump water heater and install the water heater next right to the outdoor unit for the HVAC.
We brought down our energy consumption substantially over the years starting not so far from that high figure, including swapping out racks of Sun servers for an RPi or two, and we are now slight net exporters of utility energy and with it roughly zero carbon...
I think Scott's usage is high – I think he mentions between £300-400 / month – but then he's got a hot tub, server rack as well as the cars.
We still have an ICE car and gas central heating but our combined electricity and gas bill is around £140 / month
Plan to go to EV and heat pump in our next house though
external wall insulation and triples glazing first! We did it and made winter ~10 degress warmer, and summer 15 degrees cooler. its cheaper than the solar/battery install.
I was really surprised too - our family (with electric car and a lot of tech) uses only a third of the energy used in TFA!
Still, even with our lower usage, solar still makes sense (especially with a South-facing roof) because electricity is so damned expensive in the UK :(
maybe saving money they used more - in other words Jevon's paradox https://en.wikipedia.org/wiki/Jevons_paradox
thus perhaps leading to more global warming
I can’t see any mention of hot water or cooking in the article, which may be relevant.
I was stoked at the power saving from turning off an espresso machine a bit sooner, a swapping out a nuc to a Mac mini.
Maybe there is a bit coin mining operation in his basement?
Nah, there's no Bitcoin mining, honest!
That’s about double the average household so I would imagine spending that money and effort into energy efficiency would pay off way better that solar and batteries.
The average household doesn't have two electric cars though
Yea, averages don't work well when talking about single units without any further details.
How many sq/ft is the house?
Is it filled with windows facing south?
Are they firing a continuous laser beam at the moon?
2-3x usage is actually pretty typical when looking at a single house when comparing to average. It's when you start getting close to an order of mag difference that you're an outlier.
I have an electric car, one powerwall (pre musk midlife crisis) and 5kw solar. we consumed 6mwhrs in 2025. Gas heating and hotwater, about 190w base because of networking, servers and shit left on.
I saw your xkcd history...
I'm an example more towards the middle.
In 2025 I produced 6.5MWh (solar) and consumed 12.7MWh (excluding solar production); this is a family of 4 in a 4 season climate with electric heating and a single electric car.
That was my highest year over the past 5 years.
An additional EV can really add up, especially if both people have long commutes.
They have no commutes. They both work from home. I don’t even understand why they need two cars for that.
I used about 64MWh last year, not counting what I used for EV charging (Which is on a separate meter). I also produced about 20MWh from Solar. With the EVs I would guess the total is around 70MWh.
Some of this extra is certainly my 6kw homelab + HVAC for that. ;)
From the article: "My wife and I both drive electric cars"
That probably explains it.
Yeah but they both work from home. The biggest reason for putting mileage on the car, commuting, is now out.
A single extra charge in a month can really mess the stats up.
An average EV battery is what, around 70kWh? Add in a bit of charging losses and we'll say maybe 75kWh being generous here, and that's assuming a nearly dead battery to a full charge. Doing that every month is then 900kWh, or 0.9MWh/yr. That's ~4% of the energy usage of 21MWh/yr.
An average EV gets what, ~3.5mi/kWH? An average US car does ~12,000mi/yr. That theoretical average EV would then use ~3.5MWh. Two would be ~7. But this author is in the UK, where the average car only does ~7,500mi/yr or so or a little over 2MWh/yr. So for their two UK cars, assuming they drove an average mileage in an average EV efficiency, they would likely have used something like 4.3MWh/yr for their cars. About 20% of their total electricity usage. This drops a good bit if they're really getting closer to 4mi/kWh in efficiency, which is likely if they're not driving on many highways like one does in the US.
That percentage of total usage is tiny, I agree.
We have one car and charge it quite often.
I just checked last month: 184kwh went into the Leaf. We used 557kwh in total (excluding the car charging).
We generated 1170kwh.
The key thing for me is the wild energy usage from the house. It’s a lot.
Edit: Your car energy usage calculation works out awfully close to what we use.
EV charging inefficiency typically loses 10-25% of the input energy, depending on temperature and battery level (low temps are bad, very low or high battery level also bad for efficient transfer).
It's more a stress test showing that even with unusually high consumption, solar + batteries + tariff optimisation can still materially change the cost curve
20MWh is around what my house used in both 2024 and 2025.
This number can mean wildly different things depending on the size of your house (and location).
I live in the Bay Area, CA in a 1,500 square foot house and consumed 7.8MWh in 2025 and 7.6 MWh in 2024.
Digging a bit more into our solar system data: We produced a bit over 9MWh in solar each year and it looks like our Enphase batteries discharged 2MWh each year.
It's high but it really depends on your lifestyle and appliances.
If you have a heat pump water heater and heat pump based floor heating you'll use 1/4th of the energy as the same house with resistive water/floor heating.
A house which barely passed regulation from 2010 will consume 5-10x the energy of a certified passive house.
etc.
That being said I think you have to draw the line somewhere. I'd much rather have inefficient appliances (resistive boiler/heaters) and be fully solar powered than spend 50k in heatpumps and other gimmicks that are rated for 10 years and cost a kidney in maintenance and the eventual replacement.
Heatpumps are not a gimmick - they're an excellent technology with lots of efficient and effective uses :)
Heatpumps, Shmeetpumps
Overly complex and fragile in the long run, the savings are meaningless if you're already self sufficient. I'd much rather spend the money in insulation and self sufficiency than these voodoo appliances.
That's my reasoning my new build house with plenty of land. In other scenarios it might be more beneficial to go for them.
Heatpumps are a proven technology, have been in use for more than a hundred years, and are one of the most efficient (and thereby cost-effective) ways to manage heat.
They're also technically simpler and have fewer components that can wear out. And they're a single system that works both for cooling and heating, rather than needing multiple system investments.
The majority of experts believe that its the future technology stack to manage heat, not a gimmick at all.
That having been said, always start with good insulation first.
Thwre is nothing voodoo about heat pumps. Not really that complex and not at all fragile either.
Which are famously reliable and cheap to service...
Yes, and that's why I have none.
>heatpumps and other gimmicks
Anecdotally, two of the smartest people I know love heat pumps—doesn’t Technology Connections too?
Was probably this:
Heat Pumps: the Future of Home HeatingIt depends where you live, where you get your electricity from, for how much, &c. It's an amazing tech don't get me wrong, and of course youtube tech nerds love these kind of things, no surprise here, I just don't think it's the silver bullet everybody imagine it is.
Heatpumps can now be had for less than £10k .. if you don't have to replace your radiators.
I do think more people should consider mini-split reversible AC in the UK, but the subsidy system specifically excludes it.
UK government subsidy support for air-to-air was announced a couple of months ago:
https://www.gov.uk/government/news/discounts-for-families-to...
Heat pumps aren't particularly expensive though and they can provide cooling.
Who spends $50K on heat pumps? They're not anywhere near that expensive.
A lot of people in America, sadly. Mini splits cost $250 to install in Japan and frequently $10k/head in the USA.
I'm talking about geothermal water/water installs for central heating.
No one is heating their place with air/air heat pumps besides americans who haven't figured out that heating spaces via air is shit tier in term of comfort and efficiency
> No one is heating their place with air/air heat pumps besides americans who haven't figured out that heating spaces via air is shit tier in term of comfort and efficiency
At least here in Finland a lot of people do. Very popular choice when replacing old oil furnaces (and as a "replacement" for direct electric heating offcourse)
Geothermal heatpump is something people mostly think about when building new.
Air heatpumps with the inside unit start from around 1000€ and 300€ to 500€ for the install. The price is mainly based on the size of the house (and in big houses you will need multiple or one with multiple inside units)
A fireplace for the couple really cold weeks to cut down the electricity bills are popular but people had those even before the air heatpumps so nothing new really.
Separation of concerns is the king of avoiding pricy maintenance and headaches.
You can already do most of that with a passive heat recovery ventilation system coupled to a ground/water exchanger. All systems are independent and the most high tech equipments you need are fans and a water pump
The entire country of New Zealand would disagree with you there - air heat pumps are our primary source of heating.
When your annual temperature range is -40 to 40 C (or a bit over 100 F) central air HVAC is a life saver.
I forgot HN doesn't understand humor, I'll try to turn it down next time my bad.
>No one is heating their place with air/air heat pumps besides americans
I am, and I am not an american, lol.
The rooftop solar game in Texas is strongly into scam territory. Most homes I see with panels on the roof are two story homes where you have a negligible amount of area to work with relative to interior space. There was a point where you'd have to deal with a door-to-door salesman approximately every 48h for an entire summer.
The most realistic residential installation I've seen was firmly on the ground at a ~2 acre property. The panels were much larger and heavier (i.e., capable) than what you'd typically find on a roof. It's much easier to build and maintain a solar array when you don't need a ladder/crane to move things around.
I think that it's great that we want to participate in making things better, but not every situation makes sense. When you factor in all of the downstream consequences of sub-optimal, fly-by-night installs, it starts to look like a net negative on the environment. I'm not trying to claim that all rooftop solar projects are bad, but most of the residential ones I've seen make absolutely zero economic sense.
Large scale wind and solar projects are the best way forward. You get so much more bang for buck. I'd consider investing in these projects or their upstream suppliers and owners if you want to get involved financially in making the environment a better place.
what is the scam exactly? Installing a small amount of solar isn't categorically worse than installing a lot of it. Its just smaller.
Surely it is? The fixed installation costs are spread over a smaller number of panels.
Which do you think is cheaper: installing an acre of solar panels across 300 seperate homes, or an acre of panels in one go on a solar farm?
For homes, solar car ports and pergulas look attractive if you are land constrained. No holes in your roof, and it is Texas, so more shade is always appreciated.
I think you're mixing two very different things: the tech and the sales channel
I was hoping to illustrate that without a hyper-aggressive sales campaign not as many people would have gone along with a bad installation.
Find a solar coop if you can to avoid the sales pain. They will assemble a group of homeowners and bid the entire group install out to achieve cost efficiency. Ground installs are cheaper and easier, imho, whenever possible (but depends on land availability and favorable solar insolation).
http://solarunitedneighbors.org/ | https://solarunitedneighbors.org/locations/
So people with these small installs are only saving $500 a year and not $1000?
I’ll take free $500 all day long please.
Where I am in California, there's a $30+/mo charge to connect to the grid, and the largest savings from a battery was being able to disconnect from the grid. There's lots of time I have excess power generation when I could give to the power grid, if I were connected, but I would have to pay extra to do so, so the potential goes unused.
Is delivering back to the grid economical in California? Where I'm from people disconnect solar panels on sunny days because it costs them money to return to the grid.
I'm on NEM2.0 so I can generate more than I use at peak hours and push into the grid for higher credit value than I consume overnight to charge my car.
Still, I don't see the value proposition for batteries on NEM2.
If I wasn't using _any_ electricity at my house, and I could 100% charge the batteries off-peak and push the power back to the grid at peak, I'd only be arbitraging like 5-10c/kWh * 15kWh per pack.
So, $1.50 per day, per pack. Unless I'm totally thinking about this wrong. The spread between peak and off-peak rates is just too small.
PG&E does net metering, but even at a sub 1:1 rate past your net usage it does not make sense that it costs more to send energy back to the grid
My provider wasn't PG&E, and I don't know if they do the same, but there's a fixed $30/mo service fee for connecting to the grid, regardless of how little power is used, even if its negative.
The worst that happens is you get paid back at the wholesale rate (from your bill, not live market price) instead of discounting kwh-per-kwh.
But is that rate always positive? Where I'm from during peak sun hours, the rate is negative and you end up paying money to deliver money to the grid. They do this to incentivise you to decouple your solar installation during peak sun hours so the net doesn't get flooded with too much energy.
The $30+ minimum on my bill was from a service fee, for connecting to the grid regardless of how little power was used.
Yes, you asked about California. I assume you are not in California.
Is the disconnect automatic? what happens when you're not connected to the grid but battery is full?
This is for solar only installations. People are advised to flip the breaker of their solar installation when energy prices are negative as it would cost them money if they deliver electricity to the grid. This helps to reduce strain on the grid.
It probably means that you would contribute less than cost of maintaining your grid connection ($30/mo)
Unfortunately no urban places allow you to remove from the grid.
California doesn't require households to get power service, but pretty much everywhere where trash service is available, it's required.
The reason is that California has made their grid extremely vulnerable. The grid already heavily overproduces solar so it is reasonable to have negative prices. There is no sink available.
Why do people still go for tesla powerwalls when you can get BYD batteries with 70%+ more capacity for cheaper ?
You can buy a BYD HVM 22.1 kWh for 6000 euros now (£5200) vs powerwall 2 13.5kwh for 7000 euros.
Or you can by a car instead. An MG4 costs less than 20000 euros with a 51kWh LFP battery. In addition to a good battery, it's a great car as well.
afaik it doesn't support bidirectional charging, I'd much rather cycle my standalone lifepo4 bank than my EV battery
Yes, it does. I haven't tried it as a do not have the cable for it, but the user interface for discharge is there and the manual also talks about this feature.
It's probably not ideal for running a full house (as it would require some other electronics and installations), but a couple of appliances should work.
There are several types of bidirectional EV charging, the one most cars has is about a 1kW fused connection called "Vehicle to Load (V2L)" but the one you are discussing is what they call "Vehicle to Grid (V2G)" and in those cars it supports the full input and output of the vehicle inverter.
In germany was (still is) illegal to use the car as battery… it is going to change soon though
Brand trust?
(Yes, yes: insert Musk related joke here.)
Those batteries must be connected to the internet to work, and the company could disable them anytime. Same for most of the inverters. I’m just hoping they don’t pull some nonsense like we have seen with other “cloud” devices. In that sense, I trust Tesla as much as BYD, and that is not at all.
Great read!
I am just wondering would stacking up batteries, charging them off-peak and using/selling back during peak usage be as good as this, or even better? Seems like this shouldn't be a viable scenario, but given the prices and idle capacity, it seems just investing in batteries and charging them at night, to be used/sold to the grid during the day would be as good as a solar installation.
We had an expensive solar install due to restrictions around our roof, so the solar would typically have been cheaper.
Another consideration is that battery installations in the UK are charged at 20% VAT, but if they're installed as part of a solar installation, they're charged at 0% VAT. So even if your main interest is in getting the batteries, a small solar install might make sense because of the savings.
The author pays £0.07/kWh off peak, but can export at £0.15/kWh. The author paid ~£7500 per powerwall which has ~13.5kWh capacity. Assuming full charge/discharge every night, you can make ~£1.08 per day, which works out to about 19 years to pay back.
Utilities normally consider disincentivizing this type of behavior from residential customers as one of the factors when setting their export pricing.
You can usually save more by generating solar locally and using it to power the home and charge the battery, then discharging the battery during peak hours (usually around and just after sunset) to earn the most. Obviously higher upfront capex.
Pure grid cycling is also frowned on by some utilities.
Octopus in the UK has tariffs where it basically takes over your system (ie the batteries in particular) and subsumes them into its wider activities, eg:
>it seems just investing in batteries and charging
I mean a lot of companies already do this with megawatt/gigawatt installations.
The key is peaking and grid stabilization. If you're a huge provider you can pay for all your batteries in a year or two if there is some large grid emergency and rates skyrocket.
If you're a non-commercial user, it's going to be hard because the provider rates you pay/get paid are much more likely to be fixed at a pretty low rate.
> The batteries can fill up on the off-peak rate overnight at £0.07/kWh, and then export it during the peak rate for £0.15/kWh, meaning any excess solar production or battery capacity can be exported for a reasonable amount.
Honestly I didn't know this was allowed.
I recently got a heat pump and am on a time-of-use tariff (https://octopus.energy/smart/cosy-octopus/) and have been thinking about pulling the plug on battery storage for a similar purpose (charge during the cheap hours; run the house off battery during the day). I am currently using between 40-50kWh per day - anyone have similar usage to this and can recommend batteries for this?
A word of caution: It's worth factoring in battery depreciation. That 7p→15p arbitrage isn’t "free" profit: you pay round-trip losses and you burn cycle life. If you assume ~£X installed, ~Y usable kWh, ~Z cycles to 70–80% capacity, the wear cost alone is often several pence per kWh throughput, which can wipe out most of the spread.
The only restriction placed on you is the export rate, which is provided to you by the DNO here in the UK. We had a limit of 3.8kW placed, which is programmed in to the batteries by the installer.
Octopus also have more flexible battery export tariffs if you want to explore those: https://octopus.energy/smart/flux/
I just had Solaredge battery installed in my house in the UK (Had a solaredge PV and inverter so made sense even tho it was more than other setups). If you are up for a challenge https://springfall2008.github.io/batpred/ is AMAZING and basically optimises when to charge and discharge your battery.
I've got a heat pump and think my paypack period is going to be about 6 years.
Hit me up on bluesky (in profile) if you want more info!
Thanks! I will check out Solaredge. Biggest thing right now with the heat pumps is lack of consistency of software.
Just looking at Havenwise (https://www.havenwise.co.uk/) and my manufacturer isn't supported.
Why wouldn't it be allowed? They're essentially renting their batteries and grids generally lack storage
Yeah not sure really. I thought these time of use tariffs were intended for charging EVs and using heat pumps, not charging batteries and selling the energy straight back to them later on in the day. But when you put it like that (decentralised grid storage) I guess it makes sense.
It benefits the grid to have people consume extra power when there's an oversupply, store it and give it back when there's undersupply. Why shouldn't it be allowed (even encouraged)?
Because of regulatory capture, only the big companies should be allowed to sell at retail and make profits.
So what I take away is that he is using approx 3x electricity, that I do and that is including my electric car. I use an additional 5-7MWh of heat but on a heat pump that would still only be a max of 2MWh which doesn’t even bring me to half of his usage, for a family of 4.
You can add your car to your whole-house AC bus using the Enphase bi-di EVSE, releasing this year:
The payback calculation doesn't consider time value of money. They are paying down £40K today but the savings are realized over years in the future. But they implicitly assumed the discount rate on those savings to be 0.
Yes, if you want to be super precise you have to factor in both the time value of money on one hand and inflation & energy bill increases on the other.
But very often these will roughly cancel each other out.
The US clean energy tax credit is only available for equipment installed on or before Dec 31, 2025 https://www.irs.gov/credits-deductions/residential-clean-ene...
As a result, more used solar should become available on ebay. I'm excited to see what I can do on a shoe string budget.
Don't be surprised when the answer is "not much". Apply supply and demand to electric power generation. If your grid rate is getting hiked then so is the market price of used solar.
Assuming the entire used market is efficient, which I doubt.
There will at least be a lag.
Battery storage tax credit (30%) runs through 2032, must have at least 3kwh capacity. IRS Form 5695.
https://www.energystar.gov/about/federal-tax-credits/battery...
£3,632.86/year for electricity seems wild. 17,000kWh/year is about 46kWH/day. We consume less than 3kWh/day on average.
Do you have electric heat? Do you have automobiles and do you fuel them with electricity?
We do use electric heating from time to time but it's not constant. No electric cars. Still a 15x increase seems huge.
Increasing electricity production 10x to electrify cars is not going to be achievable soon. Either via the power grid or home solar panels. Most people cannot afford to invest $40k in solar panels, batteries, etc.
Well, people who live somewhere where they need heating use more energy to stay alive than those who don't. Too bad California is so expensive because we could decarbonize the US significantly just by making it affordable for people to move there from Northern states.
Solar panel investment has slowed down substantially in Sweden. Basically, when the sun is shining, electricity is close to free. Similar situation with wind power.
Neither technology can move forward until there's a 100x leap in electricity storage costs. Like a bunch of us said 10 years ago, because we remembered high school physics.
Sweden is also extremely far north, so seasonality is a problem. Good synergy with Norway, though.
I have 5kwp panels one tesla powerwall (bought before musk had a midlife crisis) and a single electric car.
In 2025 we consumed 6Mwhr, imported 2.7 & produced from solar 5.1
I assume that OP must have electric heating to account for the extra power use, or just does huge amounts of miles. its about 54kwhr a day consumption.
Recently switched to octopus too because they have a proper api with 30min consumption updates
My electric bill was up 35% year over year from 2024 to 2025 - only two of us live here and there were no infra changes or new appliances.
I really need a solar solution but I feel so far out of my wheelhouse.
I had a good experience using EnergySage, a free marketplace that sources competitive detailed bids - it just needs your address and electric bill.
Heat Pump water heater running in heat pump only mode is a way better ROI if you’re looking to save some money on electricity.
Interesting breakdown for the UK where sunshine isn’t always plenty. If you have more sun this will be different.
Solar tracking trees seem to be an interesting way to get wintertime solar way up.
7.8kw on the roof here in Canada.
7.72MWh for the calendar year produced saving smack on $1000.
$5000 gov grant (free money)
Full remaining install cost covered by interest free loan, so we put that money onto the loan for the next 7 years, then get $1000 a year for the following 20 or more.
Complete no brainer.
Aren’t powerwalls overpriced?
How does a household use 1,500+ kWh per month? At my home, we sometimes get above 200, in summer with AC we may score 300 kWh, but how do you consume 5x of that? Is it heating?
Is your heating electric and do you have two electric cars?
No, we either walk or use public transit, and we have central heating. Yes, this explains the difference.
This setup only really works because of a very specific combination of smart tariffs, EVs, and aggressive automation. Without those, the math would look very different
Absolutely — tariff choice, storage, and automation make a huge difference.
The article isn’t claiming this setup is universally optimal, just showing what’s possible when those pieces are combined and used deliberately.
this can be disallowed in the UK, depending on their agreement either their provider. the OP is exporting way more energy than they have ever produced through solar; in effect they’re selling back off-peak energy to the grid, which is making a profit
Why would it be disallowed? That's a useful service to the grid – it's renting energy storage.
UK off-peak energy is mostly surplus of wind, while the peak is burning natural gas. Feeding off-peak energy back to the grid at peak times makes it greener.
> Having our full costs returned in ~11 years is definitely something we're happy with
Except that after 11 years the equipment will have broken down or become obsolete, at which point you have to start over.
> we've also had protection against several power outages in our area along the way, which is a very nice bonus.
This seems to be the real benefit of the setup.
The equipment doesn’t have moving parts so I wouldn’t expect it to break down so quickly.
The real surprise for me was how much having solar panels on your roof adds to the cost of roofing work. Which is a problem because the roof is likely to need repairs more often than the solar panels.
Yeah it's a tradeoff on the roof. The panels also increase the lifetime of the roof.
Solar panels are incredibly durable, there's a thriving secondary market for used panels, and we're likely to see 30-50 years of usage out of any panel created today.
Cracking the problem of making the roof out of solar panels seems like a fantastic engineering challenge. But not one with small tiles, make the roof out of the bigger cheap large panels. I would love to see startups working on that. Asphalt roofs look like crap anyway, changing to shiny panels would be a huge improvement IMHO
What breaks in 11 years? Solar panels and batteries both last longer than that.
As for your other point of becoming obsolete, why care about chasing latest fads for home appliances.
Are you sure? Lots of people are telling me that batteries only last 4-5 years tops and solar panels usually burn out before 10 years /s
I particularly love when they are telling me that my 11 year old Prius' batteries will only last 5 years before they are junk.
This is totally wrong. I work in the industry. Solar panels should last for 30 years, but they degrade in capacity by 0.5 to 1% per year, depending on environmental conditions (temp, radiation, etc). Lithium batteries from tier 1 suppliers can last at least a decade of regular use. It depends on how their cycling and state of charge is managed. If you keep them between 20% and 80% charge, they can last incredibly long.
/s is the sarcasm tag.
> Except that after 11 years the equipment will have broken down or be obsolete, at which point you have to start over.
If my calculations are correct, that setup probably lasts at least 30 years. This is not a cell phone battery and panels do not degrade that fast.
Great writeup!
Tldr; their full costs of the system are returned in 11 years.
Whether that's good depends on your perspective and assumptions, you can take a look at opportunity costs.
Imagine you have 100k for say 30 years, and you have three choices: 1. put it in a UK government bond at 4.4% -> 100 * 1.044^30 = 363k 2. put it in the S&P500 (dividend reinvested) at nominal 10% rate -> 1.7 million 3. buy a system that can't be made liquid after 30 years, but returns 11k flat per year = 330k.
1 is very safe and virtually guaranteed. 2 is considered less safe, but over 30 years broad based stock indexes are far less risky than short-term stock investing.
3 is perhaps the most difficult to make assumptions, as its house-tied and operational. Switch houses for any personal reasons, and you'll not be able to fully make your investment liquid and recuperate it. Blow an inverter, see panels degrade and replacement costs must be factored in. This pushes down the final cash position of 330k.
We could be generous and say that the 11k flat savings will increase, as electricity prices rise. Prices grew by 5% yearly in the UK, under that rate so the 11k savings today would grow to 47k annual savings in year 30, and total savings over 30 years would be 870k, pushing up the final cash position, but still not getting close to a long-term stock index investment.
But even that's somewhat generous for two reasons: one is that the 5% inflation was unnaturally high due to the EU's energy crisis from the Russian invasion, and not necessarily indicative of the next 30 years. Various countries in the EU are also curtailing renewable production because there's too much of it (precisely during the moments solar systems were making their biggest profits < 2020, you since see curtailment growing), and with more storage coming online rapidly the profits from their battery system are expected to decline, not increase. -- generally speaking, solar energy producers were more profitable a few years ago, and are becoming less and less profitable over time as competition from cheap panels undercuts them. Many countries have begun to cut the reward from exporting back to the grid from the retail prices of €0.30 to the puny wholesale prices of €0.05 and all countries are expected to go down this road eventually.
On the other hand, AI seems likely to push electricity prices higher for a long time... but it's the newest and biggest question mark compared to the other assumptions we've made above.
It's crazy how power hungry UK homes are, or maybe it's UK power consumption habits in general.
I use about ~300 kWh/month. A little bit more with AC some times of the year. What are you even powering with 15000 kWh?
The OP is a significant outlier - the UK average is around 7.4kWh/household/day[0], or 11.2kWh specifically for large households.
[0] https://www.britishgas.co.uk/energy/guides/average-bill.html
Are you commenting on this article? This person is in the UK. You can see it on their domain, their calculations using pounds, and then mention living in the UK multiple times in the "Our setup section".
I did try to make it clear in the article.
We're powering 2 x EVs, have two adults working from home full time, I have a server rack under the stairs, and we have a hot tub outside.
They explain in the article.
So TLDR: spend 40K up front to save 3K per year - could be cost effective depending on the functional lifetime of the tesla powerwall.
I've been following a story where Elon Musk's xAI is building an 88 acre solar farm next to its Colossus data center near Memphis TN after public outrage due to running 35 methane gas turbines without a permit, which increased NOx emissions enough to allegedly impact health:
https://techcrunch.com/2026/01/12/trumps-epa-plans-to-ignore...
88 acres = 356,124 m2
4.56 kWh/m2 per day solar insolation (4.5 is typical for much of the US)
4.56 kWh/m2 per day \* 356,124 m2 = 1,623,924 kWh/day = 67,664 kW = 67.66 MW average
1000 W/m2 \* 356,124 m2 = 356 MW peak
30 MW is still only 10% of the the 300 MW used by the data center. But there's lots of land out there, so roughly 1000 acres per data center doesn't seem that extreme to me. That's a 4 km2 or 1.5 mile2 lot, or about 2 km or 1.25 miles on a side.
Basically every GPU server uses 1 kW (about 1 space heater), which puts into perspective just how much computing power is available at these data centers. Running a GPU continuously at home would need 24 kWh/day, so with > 20% efficiency panels that's 4.5*.2 = 0.9 kWh/m2 per day, so 26.67 m2, so at 2 m2 per commercial solar panel and assuming that my math is right: that's about 14 panels considering nights and seasons.
It's interesting to think just how many panels it takes to run a GPU or space heater continuously, even when they put out 500 W or 250 W/m2 peak. And how cheap that electricity really is when it's sold for on the order of $0.15 per kWh, or $3.60 per day.
I've found that the very best way to save on your electric bill is to have a few south-facing slider doors and windows, which is like running a space heater every square meter of window. There's just no way that any other form of power generation can compete with that. Also, I feel that we're doing it wrong with solar. This analysis shows just how much better alternatives like trough solar and concentrated solar (mirrors towards solar panels) might be cost-wise. On an ironic note, solar panels now cost less than windows by area, and probably mirrors.
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This is indeed nice for a well-to-do home. But there is a tragedy of the commons issue here.
The grid needs to be up 24/7. And while peak usage is just that, the grid capacity still needs to support peak usage.
This can theoretically be done using batteries but not for an extended amount of time. To say we can have batteries for 2 weeks of normal consumption is highly improbable.
The metals do build those batteries do not exist. Or put in a worse way, the mines do not exist.
An off the cuff calculation of costs and the massive amount of batteries required in the context of Sweden can be found (you need to translate) here: https://www.tn.se/naringsliv/40181/utrakning-60-globen-batte...
In other words, 60 full scale Globen arenas of batteries to replace current Swedish nuclear production.
So for small houses these investments can make sense currently. But from a larger perspective it's not that interesting.
Residential solar with batteries greatly aids the grid and reduces costs for the entire system.
> The metals do build those batteries do not exist. Or put in a worse way, the mines do not exist.
Lithium and sodium, the two most promising battery metals, are not usually mined, though in Australia I hear there is mining. It's more of a brine process. All across the US, frackers are finding that all that water they are pulling out is a fairly rich lithium brine.
The amount of metal needed for 2 weeks of batteries is pretty trivial compared to the system we've built for extracting fossil fuels, and iron, etc. The bigger demands for electrification are acutally copper! Gotta wire everything....
Grid batteries on the GWh scale make a ton of sense financially and environmentally, and are revolutionizing the grid. Never before has the grid had a way to store electricity on a grand scale, which changes the entire nature of the beast. It's was one of the only massive systems we had where there wasn't buffering!
With storage, we can alleviate congested transmission without super costly transmission upgrades. On exist lines, we can the usage massively, reducing costs, because now we can buffer across time to shave off the peak demand.
Batteries are easy to build, environmentally friendly, and like a swiss army knife in their number of applications. We will be producing TWh of batteries a year in modern economies, and they last ~20 years, meaning that for the foreseeable economic growth in the coming decades, we'll easily have a peta-watthour of battery storage in use at a time.
I don't agree. Lithium and Copper are mined and given electrification scenarios there is a projected supply deficit: https://www.iea.org/reports/global-critical-minerals-outlook...
Those prices are outdated now since practically all metals are surging.
There has indeed been great growth in battery capacity but it's as I said nowhere near able to supply a country like Sweden during the winter. It is off by orders of magnitude. We need 5TWh for that. It is not going to happen any time soon.
I understand California is different. Still, one would need to do these risk scenario calculations. Have they been made?
I know California has rotating blackouts already as it is. I really don't have any idea how people find that acceptable. If it happened in Sweden the government would be replaced on the day. It would be a real disaster.
I will be a bigger believer if a state like California can actually show its possible.
For sure I hope technology improves but the current ideas of solar+battery are simply highly unlikely.
What gives you that impression? Unless you're looking at the pre-9/11 grid powered by Enron™, rolling blackouts aren't a big deal in California. I think since 2001 there was a single 2 day event limited to certain regions, I don't know anyone personally who lost electricity due to rolling blackouts.
The CA grid has also scaled up battery storage surprisingly quickly. A few years ago it was in the single digit mWh, not really a meaningful fraction of the grid. Now it's measured in gigawatt-hours.
You are right. Not sure where I read it but it was clearly wrong.
Still, I think the grid is very vulnerable with that amount of weather-based energy. If there can be enough batteries to sink all that power generated and have it during evening til morning then that's great.
Perhaps that _can_ work in California, I really don't know what an acceptable level of storage would be. That is, how many days worth of battery power you'd want in case of bad weather conditions.
Your link does not support the idea of a supply deficit, at least that I see. Propel panicked about lithium under supply, prices surged and didn't even affect battery prices much, and now we are in oversuppply. The worst that can happen is lag time between demand increase and supply match, and there are substitutes for all key metals for most applications, even copper.
Every country will have to figure out how to supply its own power, but Sweden's seasonal variation in renewable resources is not likely to be fixed by batteries, even though batteries will be abundant and in massive supply throughout the rest of the world. If Sweden can't figure out, or merely can't, take advantage of great cheap new technology, they will be at a disadvantage compared to countries that will
> I know California has rotating blackouts already as it is
You don't know that because it's not true. Due to planning not taking into account climate change, there were a few days with demand above expected ability to provide capacity, but there were no blackouts because people were asked to voluntarily cut back on excessive cooling. That mere ask was more than enough to get through the few days. And it was fixed the next year, by what? By batteries! Adding nuclear wouldn't have helped, but batteries were the perfect solution. Perhaps nuclear can help Sweden, but it will be far more expensive than the solutions available to other countries.
It is quite funny that what I thought was US propaganda has been spread to Sweden for repetition. Even including the IEA report that doesn't say what people claim it says!
I read through the IEA document when it came out, and didn't find anything like what you say, because I remember people claiming things like you say and I couldn't find anything that supported it. If you have quotes, pages, etc. please point to them. The closest contention is also in the summary:
> For lithium, near-term markets appear well-supplied, but rapidly growing demand is expected to push the market into deficit by the 2030s
We've been pushed into lithium supply deficit in the past, and quickly got out of it. This is not a statement that there's not enough lithium or copper, rather that the market wants more than they currently see in development. The IEA document doesn't say anything about electrification not being possible, it's meant as a signal to policy makers to ensure that new copper mines can open up in the future, and that there's great opportunity for countries that do that.
When people are making 100 billion dollar bets on factories that use copper as an input, they are also ensuring their supply years out, which enables development of the necessary mines.
Say the worst case predictions from the document come true: there's a price spike in copper due to there being greater demand than supply. That drives up prices, which spurs on more copper mine development, but the existing copper is still being used to make the energy transition. The electrification trend continues, but just at the rate of current copper extraction! Clever people find substitutions for the electrification challenge. Or people substitute inferior and more expensive non-electrified traditional industry rather than the new tech.
There's a fundamental difference between metals for infrastructure and fuels like oil: if you have a fuel supply shortage it causes inflation, economic contraction, etc. With a shortage of copper and increase in prices in devices that use it, people wait a bit to replace that old appliance (maybe), or use an alternative that perhaps requires fossil fuels.
> Most grids aren't built that way anyway. The residential units are sinks, not sources. In Sweden we don't even have much solar power but already there have been policies aimed at reducing grid exports from residential units, because they are mostly redundant and even harmful.
Grid engineers are extremely conservative, and don't want to learn anything new, and always resist at first. Until somebody shows them how it works, they claim it's impossible. That allowing individual homes to feed back to neighbors will break everything. Then people do it and its fine. Then grid engineers claim that at 1-2% of variable supply the whole grid will come down. Then 1-2% of supply is variable solar and everything is great, so the engineers claim that 5% is the new limit. Or 10%. Or 30%. They are living in the past, don't want to learn anything new, and assume that anything new is impossible. It's a natural feeling for engineers that should be very conservative, but also incorrect. They complain about needing inertia, reactive power, without realizing that all that is quite possible with existing tech! Until a proper cost analysis is done by independent people that are fully honest about the costs, I wouldn't trust anybody saying that allowing a home to feed back into the grid is harmful. Plus, batteries negate the need to feed back into the grid at all. Keep homes as 100% sinks, just pulling down electricity far less. Or put batteries in homes to reduce their peak draw from the grid, so that all the rest of the grid can be far cheaper. There's so much potential that gets ignored just because batteries are new tech.
I don't see where anyone is proposing this as multiple-week storage for the whole grid?
That's why you're investigating hydro storage:
https://www.ess-news.com/2025/02/11/fortum-explores-new-pump...
What makes you think I need batteries for 2 weeks of normal consumption?
Nobody needs that, but from my point of view batteries will be so cheap and abundant that we will likely get to having 2 weeks of storage just sitting around the grid or rolling on wheels.
People always underestimate where exponential cost decreases will take us. Current battery production grows by 10x in a mere 5 years. In a decade, the time it takes to build a nuclear power plant, we will grow our battery production by 100x. Not enough people take this seriously, or even know that the trend exists.
We practically don't see the sun in northern Europe during winter. And yes, the wind might not blow either.
I consider 2 weeks of supply a bare minimum.
How would 2 weeks of battery help you in that situation? The winter lasts a lot longer than 2 weeks. So after 2 weeks of no sun, wouldn't you be just as screwed as if you had 1 week of battery storage?
There's going to be a bloodbath in that market in the next years. There are a lot of battery producers and most of them are not producing at full capacity. At the same time, manufacturing cost is dropping as well.
Some battery makers are producing batteries at a cost level of around 60$ per kwh. At that cost, the 16kwh battery would come out below 1000$ (not the same obviously as the product price). Sodium ion might push those prices even lower. Below 50$ soonish and eventually closer to the 10-20$ range in maybe 5-10 years. At that point we're talking a few hundred dollars for a decent size domestic battery. You still need packaging, inverters, etc. of course.
But the ROI at anything close to those price levels is going to be pretty rapid. And it wouldn't break the bank for households across the world. Add a few kw of solar on roofs, balconies, etc. It won't solve everyone's problems and certainly not in every season. But it can help reduce energy bills in a meaningful enough way. Even in winter.
Also worth pointing out: most of the US is south of Cornwall. The Canadian border runs roughly at 49 degrees latitude. Cornwall is the most southern point in the UK sits at 50 degrees. If it can work there, most of the US has no excuse. Also, the UK isn't exactly well known for their clear blue skies. Even people in Scotland much further north manage to get positive ROIs out of their solar setups.
I installed a 16.5kWp ground-mount array a month ago. I live in the US Northeast, in a mountainous location that means we get late sunrises and early sunsets. Nevertheless, based on my one month of data, it looks like we can generate all the power we need for our household on a sunny winter day, excluding electric vehicles. Even on overcast days, we can sometimes offset a significant portion of our usage. My locale does not have time-of-use rates, so there’s no point trying to do arbitrage for electricity prices. So right now I just have our battery configured for backup. My hope is that during the summer months I can reconfigure the system to use the battery to reduce grid reliance instead.
The expiring tax credits were what forced my hand. I’m the kind of person who likes to install things himself, and I probably would have gone that route for solar too, because the materials costs (sans battery) aren’t even half of the total cost.
Here in Europe, we got more than a month's worth of foggy, cloudy weather (something that looks like will keep being a thing), which is something I became painfully aware of as an owner of a solar setup.
No amount of battery banks can tide over such a long stretch.
By the way, let me ask you - considering your location, you must be getting a lot of snow, how do you deal with it, is it a problem? Panels are quite hard to reach on the roof.
I've got a similarly sized ground-mount array, and I push the snow off with a triple-telescoping aluminum pole with a large squeegee on the end. An actual snow rake might be better, like the one you describe, but my setup gets it done. It takes some effort, but it's worth it to be able to collect the solar energy that would otherwise just reflect off the snow for days.
Maybe you can even forward-bias your panel, and make it generate some heat off the battery power. (It may even glow a tiny bit.)
Where in Europe? Between Spain and Denmark there is a lot of variance in temperature, sun and rain...
Talking about the weather "in Europe" is like talking about the shoe size a family of 10 wears.
One thing to remember is as it becomes more widespread line costs will go up (assuming they are subsidized by kwh use, which they generally are) and no-sun power prices will increase as it's the only time when the grid needs power from non solar producers and they still need to cover cost incurred while they're not producing.
That will push the economics towards completely off grid systems as more people adopt solar, so if people are planning it for themselves they should probably consider that it will make sense to expand their set up in the future and that there might be a price crunch due to higher demand because of larger systems coupled with more people wanting to switch.
My partner works in the field and we once talked about this. I think the idea is that individual consumers’ and businesses’ batteries can serve the grid as needed. For example, if your car is fully charged and you don’t need it today, it can top up local needs.
So I think the writing isn’t on the wall yet for line price going up, although I’m of course talking of a) Belgium, and b) a future that could go wrong if utilities don’t fund smart metering.
That sounds quite good, but you have a massive installation. Did it pay for itself by now?
An interesting possible is the grid becoming smaller. Neighborhood scale.
In many places from Central Europe and further north dealing with arctic cold spells and dunkelflautes are near impossible for a home solar and storage setup.
But you also don’t want to pay for a continental scale grid the remaining 51 weeks.
So in your neighborhood add some wind power and a good old trusty diesel/gas turbine running on carbon neutral fuel and keep the costs to a minimum.
This is addressed by crowdsourcing generation and storage to household batteries. Surplus energy is banked locally instead of being dumped on the grid. The utilities buy it back from homeowners at wholesale rate under demand response programs when they can't meet demand.
Many cities in north america you cant get occupancy without grid tied electricity, so every house incurs the coat of bas government policies on transmission. Its why i havent bothered with this yet. The optimal setup for here is natural gas generator, some battery and some solar given how stupid the fixed charges are here but you cant live in your house if you disconnect from the grid (even better would be for fuel cell manufacturers to offer something sized for a house so i can get hot water put of it as well and a silent unit)
I'm not so sure. There are a lot of large-scale applications that would gobble up battery supply if it hit a certain price point. Grid-scale storage and datacenters, for example.
If prices for residential gear falls too much, I expect the manufacturers would just stop making it and focus on the commercial options instead.
IMO, there's close to no bad usecase for batteries. In almost all their applications, they end up spreading out power consumption favoring cheap energy for expensive energy.
If a datacenter installs a solar array + a giant battery pack for their power, that's much better than them heavily relying on a natural gas plant to generate power when the lights are out.
The commercial options would fall further in price probably than consumer prices. If you buy in bulk, you do research to find the most cost effective options. That's a common pattern with many things. I don't see why batteries would be any different. If anything, I'd expect consumer batteries to have higher margins. Tesla batteries are a good example probably. At those prices, a Tesla car would be unobtanium. Obviously they charge a lot less for batteries that go in a car.
The reality is that many battery factories might be operating at 40-50% capacity only. Exact figures are hard to come by but there are lots of warnings about over production, surpluses, etc.. That spells a lot of trouble for some of the newer battery producers promising more efficient batteries. Because unless they price match, they price themselves out of the market almost immediately.
Why does it have to be zero-sum?
Why not commercial demand creates the economies of scale that bring the residential stuff down in price with them?
Majority of the world's battery manufacturing capacity is dominated by just a small handful of players:
https://en.wikipedia.org/wiki/List_of_electric_vehicle_batte...
Just 11 companies control 90+% of manufacturing capacity, I think they might need to adjust their ambitions in the face of demand, but I think most of them are too big to fail.
Companies like Schneider electric have systems for 25-50% the hyped brands but they don't provide batteries.
This is the company that owns APC so its not like theyre new or untested. They just don't bother with brand awareness
Its weird to read about Schneider Electric not bothering with brand awareness. They aren't a household brand, sure, but they are well up there with Siemens and the like in industrial/b2b sector and their marketing budget is allocated accordingly.
All they did was buy up everyone's else brand and put their brand over it. Modicon PLC's, Magnecraft relays, etc.
I suspect the traditional grid operators will fight this very very hard.
IIRC, the original idea was that they would pull older batteries from circulation when their capacities dipped, and then repurpose them as powerwalls, an application where weight is irrelevant.
This was back when they expected the batteries to plateau at ~80% capacity after a few years, and they had battery swapping on the roadmap, so they needed to plan for a future where they had a steady supply of batteries that car customers did not want.
The idea took hold, but the batteries lasted longer and swapping didn't pan out, so now they are competing with themselves for battery supply.
Electric car battery degradation has been super interesting, in that they are going way further than people thought they might. Jonny Smith on youtube bought a 300k+ mile Tesla and the battery is at like 75% health.
As far as I can tell if your battery isn't air cooled, it can go a very long way
There was some research[1] that strongly suggested that varied use makes them last much longer than the steady use that most battery tests do. That is, bursts of high-current draw followed by moderate draw etc vs the constant current load typically used when evaluating battery performance. From the paper:
Specifically, for the same average current and voltage window, varying the dynamic discharge profile led to an increase of up to 38% in equivalent full cycles at end of life.
This was unexpected, hence explains why they fared better than predicted.
[1]: https://www.nature.com/articles/s41560-024-01675-8 Dynamic cycling enhances battery lifetime (open access)
Without knowing anything about it, I would posit that degradation accelerates the longer the battery is kept above some threshold temperature.
So, a heavy-burst+low results in a sudden high temperature then settling into a lower temperature. Steady flow keeps it at moderate temperature (above threshold) for a long time.
Any idea why swapping didn't pan out for Tesla? My understanding is they are doing that in China.
What do you mean? It did pan out for Tesla. Faking a single demo granted them 75% more ZEV emissions credit government subsidys [1]. That increased their profits by hundreds of millions of dollars.
All they had to do was go on stage and “swap” a battery without any clear video of the process and never “demonstrate” it ever again.
This is a company known for faking prominent demos like the FSD demo (where it crashed into a wall during filming), the solar roof demo (where they used regular roof tiles and claimed they were solar panels), the optimus demo (where they were teleoperated), etc.
Assuming they even did a battery swap, for which the official demo presents no clear video evidence, preferring overhead views over a close-up of the process or a glass enclosure to see the inner workings, it was at best a one-off custom-made device at the time. The one battery-swap station they claim existed has zero stories of any actual battery swaps, instead only evidence of it operating as a regular Supercharger [2].
[1] https://thewaroncars.org/episode-88-tesla-is-a-fraud-with-ed...
[2] https://slate.com/technology/2022/05/elon-musk-tesla-twitter...
Cool. Then if you are not lying, then it should be easy to present a clear video demonstrating the automatic battery swapping machine in action and swapping out a battery in 90 seconds as claimed in the demo.
The bigger risk is you need a standard battery pack. Sure you can put 3 in a truck or something, but you lose all the space that a standard battery size wouldn't fit but you can cram a cell in. Electric car design is about stuffing batteries where there is space - you need a lot of cells, but the individual cells are small.
> of unknown provenance
I don't understand the comment. Of course they know where the batteries come from. They know everything about the battery.
As long as you can always swap your battery again I don't see the problem
As long as the average battery health in the system is like 90% and the minimum is say 80% why would you care if you're getting a new battery every few days?
If anything it removes a big cause of depreciation from your car
Eh?
In some mysterious future where swapping EV batteries during a road trip is a normal activity, then the battery packs won't be living in a vacuum -- their status can be known. Whether it is known by reading the pack's own electronics, by status reports from connected vehicles and charging stations, by direct measurement, or by some combination of these things: The status is knowable. It doesn't have to be a big ball of mystery.
How much value the marketplace finds in this health status is a different question. And this question is one that we cannot yet know the answer to -- this is not a reality that we presently live in.
We can speculate about how that potential future may be shaped, but that kind of speculation is kind of meritless since that version of the future may never actually happen (and at the present, it sure does seem very unlikely to happen any time soon).
> Any idea why swapping didn't pan out for Tesla?
~~Two~~ Three things:
1. California changed the rules shortly after Tesla demonstrated their swap station, which practically eliminated the tax credit for battery swap (at the behest of lobbyists for Toyota, who were backing Hydrogen Fuel Cell technology). Specifically, the credit would be prorated by the percent of “fast refueling” sessions a car did, so EVs primarily charged at home received almost nothing while HFCV got the full credit. Building swap capability adds complexity to the car (think about all the fluid connections), which isn’t worth it without credits.
2. It was also around this time that a Model S ran over an anvil (or something) which punctured the pack and started a fire. In response, Tesla added an aluminum battery shield, which further complexifies swapping and was probably the final nail in the coffin.
3. The logistics of storing your very expensive battery (so you could get it back later) basically make the system unworkable. When the Tesla swap station at Harris Ranch (you can still see the former building, next to Harris BBQ, which currently houses the restrooms) was operational, you had to make a reservation some hours in advance so that Tesla could have a pack ready and be ready to take your pack to/from storage.
3a. Gresham’s Law. Without eventually returning the pack to the original owner, there is an adverse selection problem: people with very weak packs will gladly roll the dice on a swap, but those with brand new packs are reluctant. So the average quality of packs in the swap network will quickly decline creating a death spiral.
3b. You could probably fix 3a by leasing the battery (or selling battery-as-a-service) but car buyers mostly don’t like that, especially back in 2013.
In addition to all of that, it just doesn't outcompete recharging in the end.
Even if the swap station got to where it was hoped (no reservation needed, automated, drive in, swap, drive out), you'd have a choice between a ~5 minute stop at a swap station, or a ~10-20 minute stop at a charging station. The swap station is always going to be more expensive since it's inherently more complicated, so you're spending more to save a few minutes. And when you stop at the swap station you can go answer the call of nature and grab a snack while you wait. If you want to do either of those anyway, then visiting the swap station means you'll do the swap, then go do those other things, and probably not save any time at all.
Charging time just isn't that much of an issue at this point. I've been driving a Tesla for a decade at this point, with thousands of miles of road trips around the eastern US, and I've never found myself wishing for battery swap infrastructure. Newer cars charge much faster than mine does, too.
I could potentially see value in a car with a smaller built-in battery for use around town, and an empty space for a larger battery, that you rent from swap stations for longer road trips. Of course, that doesn't work with anything on the road today.
Probably because the economics just don't make sense here. You'd have to have so many compatible cars on the road, driving all day with no opportunity to charge. I'm having a hard time imagining a place I've been to in North America where that'd seem logical.
> they are doing that in China
Are they actually doing that at scale?
From the country that brought you mass wastage of bicycles, now we get battery swapping.
This is pretty much just a "gamble by deploying as quickly as possible making our system the standard if it catches on" type of investment.
They have a 30% gross margin, they're just soaking up the federal US tax credit (which is also 30% for battery storage and extends through 2032).
Alternatives: https://electrek.co/2025/12/28/opinion-its-time-to-start-rec...
A few of the alternatives have been reviewed by Will Prowse as well. His YT is a treasure of information. https://www.youtube.com/@WillProwse
The crazy thing is you can buy a 69 kWh battery from Tesla for $36,990, and it comes with a whole car too.
Exactly! This is how the future should be: solar panels + portable huge battery arrays doubled as vehicles + grid as backup.
In the UK, where the OP is from, the equivalent of the battery you linked is available from Fogstar for £1850 (includes 20% VAT), shipped. Without the VAT that works out at ~$2000. A compatible high end 9kW inverter is available for around £1200.
The ROI is really attractive once you look past the overpriced kit.
It is interesting to compare to V2H systems.
I believe Chevy offers V2H on all 2026 Equinox EVs. Enabling this needs their V2H Enablement Kit and I believe you also need their PowerShift Charger. That would be around $38k for a 2026 Equinox EV LT, which has an 85 kWh battery, $6300 for the V2H Enablement Kit, $2000 for the PowerShift Charger. Installation via the company Chevy says to use is $2000-5000 according to the net.
That brings us to $51-52k, and would give 70ish kWh of usable backup capacity. That's around $750/kWh of capacity.
Getting that capacity with Powerwalls would require 5 of them and cost quite a bit more.
Plus, with the V2H approach when you aren't having a power outage you can use it as a car. :-)
You're comparing the cost of a battery with a full system. That 16 kWh battery requires a ~$3000 inverter to go along with it.
Well, the math still maths, right?
I am writing this off grid, using about 15kwh of batteries and a $1200 (6kw) inverter. My entire system puls panels and racking those panels, plus wiring some un-powered shacks was about $10k, though I did the work myself (which would probably hae been another 3-5k if I could have found someone to do it.
> which would probably hae been another 3-5k if I could have found someone to do it.
Yo. If you can find an electrician to stop by my house and turn a light switch off for less than 1000$, please inform me. I got a quote for 25k$ to install a system that size, and that price. City code has me by the balls: I can't modify my main panel without inspection, the inspector won't show up without a licensed electrician, and electrician wants the labor. I pointed out that we're talking 8 hours of labor — call it 2500$, lawyer money — and he was like "what's your choice". I'm in Texas.
Weird. I'm in PA, and my electrician quoted me a flat fee of $100 for replacing my outlets with GFCIs (each).
To get a journeyman electrician license in Texas, you need to have 8000 hours of documented on-the-job experience working under a licensed electrician[1].
So you'd need to find an electrician who will let for you work them on the weekends, and if you work 8 hours every Saturday and every Sunday, then it will take you 500 weekends.
A residential wireman license only requires 4000 hours[2], but I'm not sure if that kind of license would be good enough for the inspection.
---
[1] https://www.tdlr.texas.gov/electricians/apply/individuals/jo...
[2] https://www.tdlr.texas.gov/electricians/apply/individuals/wi...
"licensed electrician" is also timewalled behind a lengthy apprenticeship.
From google's llm "..requiring 8,000 hours of on-the-job training (OJT) under a Master Electrician .."
so even if you could pass the test you still don't get to become licensed until you've paid your dues in terms of time.
This right here - I have been investigating getting my own contractor license for DIY work on a property I own that must be permitted but city will only issue permits to licensed contractors. Took a practice test for the exam on a whim and nearly passed it without studying. Anybody seriously considering DIY'ing the install of something like this probably could get a license without a lot of work.
"Freedom for me, rules for thee". Texas has always been a cesspit of political kickback. I mean ... not Illinois or New Jersey, but annoying enough.
From what I quickly checked you can modify your own home there is an exclusion for doing electrical work on your property - seems like main panel would be somehow excluded from what qualifies as "yours".
Hoss I am sorry to hear that- I have literally no idea what electrical costs, as I've been doing it myself. If you're living close enough to other humans that the can observe and complain, then we're not really in the same situation.
But that doesn't really change my point, does it? Like, if they are installing $6k worth of equipment and materials, then that's what the up-thread points was about paying 10K more for tesla-branded equipment, right? I get that at a certain point the labor makes the cost of materials less of a deal, but my point was that my battery+inverter+panels+material is still less than the equipment they are describing.
That's fair.
Better comparison:
Author's config:
3x Powerwalls + inverters = 40 kWh
4.2 kW array
£39,360 = $53k USD
Alternative:
EG4 18kPV Hybrid Inverter = $5000
3x RIUXU = $9600
10x Trina Solar 435w panels = $1580
Cabling, installations, etc. = $5000
Total = $21k
It's not even close...
This is still not an accurate comparison. I'm not a Tesla fanboy but of all of the major players in the non-diy game (Enphase, Franklin, Tesla, Sol-Ark) they provide the best value for money, and are impressive pieces of equipment.
The EG4 18k has 11.5 kw backfeed capability, with a rather pathetic 65ish amp in-rush. Obviously 18kw usable solar capacity(they technically let you land up to 21kw, but only 18 is usable).
The Powerwall system you outlined can take 60kw of usable solar input, has 34kw standing backfeed capability, and a whopping 555 amp in-rush (not a typo, it's 185 amps per unit).
Not to get in to warranties, etc.
Inrush is exactly what it says it is, it's inrush current. When you have a sudden surge on something, that's inrush. Lots of appliances in your home have a large inrush, much larger than the breaker they're on. Inrush happens faster than a breaker trips, which doesn't matter when you're on the grid and the inrush is lower than your mainbreaker, it matters when you have an inverter in the way with a passthrough limit and an inrush limit. Typical central HVAC units have LRA over 100 amps.
If we're talking about 'doesn't even matter with a 4kw array' well, hell, how the hell you gonna charge ~40kwh of battery with solar array that nominally produces 20kwh a day on its best day, assuming all conditions are perfect?
Backfeed is what the inverter can push out from the battery to the home. It's the size of the tube coming from the gallons of water reservoir. EG4 18k has a tiny tube, no matter how much battery you put on it. Like emptying a 50 gallon drum with a drinking straw(and with the 4kw array, filling it with a 12 oz cup).
Inrush is surge capacity. Starting a big motor like an air conditioner can require 2x or 3x the continuous running amps, but only for a few seconds.
Yah, check this one out.
https://www.docanpower.com/panda-52v-942ah-48kwh-prebuilt-pa...
I actually own three of 15 kWh versions :)
They are cheap and they work but they're not UL listed...so they dont go anywhere near my home.
That's not really apples-to-apples comparison. The Tesla batteries are AC coupled so they work with an (AC coupled) microinverter array. For a DC coupled battery you have to have a hybrid inverter and DC couple the batteries.
Your point that they are overpriced still stands though.
Ya as someone else pointed out, powerwalls essentially have an inverter built in. But this is really dumb to have inverters tied directly to each powerwall battery. This is like anti-scale.
A small thing I want to remark is that at that price, a Model 3 costs less than 3x, and has more than 3x the battery capacity.
Considering DC connectors on EVs provide a direct electrical connection to the battery terminal, and the charge-discharge circuitry in residential hybrid solar inverters can handle them just fine (provided it supports the voltage ranges, but people did this).
I think it's an enormous missed opportunity, that the most common charger standards don't support this (CCS2 doesn't, Chademo does, no idea about NACS)
If this was a thing, I think it would completely reshuffle the EV market, I don't know how used residential batteries depreciate, but I doubt they lose more than half of their value in 5 years like EVS do.
The Ioniq has the ability to provide battery power out so you can plug your house in.
I'm talking about something a bit different - the Ioniq uses a V2L, which means it has an onboard inverter that generates AC mains voltage through the plug, and can be used to provide equipment directly.
What I'm describing is using the cars DC charge port and connecting it to inverters DC battery port.
For what it's worth, Tesla PV/batt inverters are bad, almost as bad as the Chinese manufacturers mentioned ITT. PW3 has very high failure rate ~10%+RMA, not good enough IMO to be in the path of power at my house.
(Their motor inverters are world-class, but totally different topology)
You might find https://www.basepowercompany.com/ interesting, 25kwh battery for $700 down and $20/month
Now they are overpriced but up until 2022/3 they were the best value unit.
I think "overpriced" depends a lot on what problem you're trying to solve
A statement so vague as to be tautologically true.
Powerwalls don't uniquely solve any problems other brands can't do.