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 $5k and it's still cheaper and you wouldn't need an additional inverter every time you add a battery.
Some battery makers are producing batteries at a cost level of around 60$ 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.
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.
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.
Talking about the weather "in Europe" is like talking about the shoe size a family of 10 wears.
Fortunately I have a ground mount. The bottom row is roughly at waist height. I can (and have been) sweeping the panels off with a large push broom. Because my array is so large, I can only reach the bottom half of the array. But this usually is enough. When the panel starts to generate power, it also tends to heat up; the snow on the top half then often slides off on its own.
I might invest in a longer broom. It is not uncommon for people here to own “snow rakes” to remove large snow loads from their roofs. These usually have a rubberized “rake” with a very long aluminum handle. Or the novelty of this might wear off and I’ll just let the panel do its own thing. It is pitched rather steeply (close to 45°) and based on my observations of my neighbors, panels tend to shed the snow on their own eventually.
If prices for residential gear falls too much, I expect the manufacturers would just stop making it and focus on the commercial options instead.
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.
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.
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.
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.
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.
This is the company that owns APC so its not like theyre new or untested. They just don't bother with brand awareness
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.
As far as I can tell if your battery isn't air cooled, it can go a very long way
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)
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.
However they also note more material studies are needed to understand these mechanisms better.
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...
I don't understand the comment. Of course they know where the batteries come from. They know everything about the battery.
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
Of course this isn't a new problem. I know people who own their own welding gas tank - but they always swap the tank out. The place they swap at somehow handles when the tank needs to be re-certified - and people don't ask questions.
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).
Tesla did briefly operate a swap station at the site of the Harris Ranch Supercharger until California changed the rules.
There are several reports from people who used it on teslamotorsclub.com, and I saw it with my own eyes.
Hilarious that your source is Ed Neidermeyer. Perhaps the only thing more impressive than Elon’s lies about the state of self driving are Ed’s lies about how Tesla is going bankrupt Any Day Now.
It’s ok though, Ed’s stock manipulation antics enabled me to stuff my IRA with Tesla shares (since sold, when Elon went nuts) and make a nice little headway on my retirement savings.
~~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.
> they are doing that in China
Are they actually doing that at scale?
> As of June 2024, Nio had installed 2,432 power swap stations in China, including 804 along highways, representing the largest battery swapping network in the country. Nio aims to expand to 4,000 stations globally by 2025. By February 2025, Nio had 3,106 battery swap stations in China, with 964 located along highways. In January 2025 alone, Nio added 111 swap stations and provided 2,949,969 battery swap services, averaging 95,160 daily.
https://enertherm-engineering.com/chinas-battery-swap-revolu...
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.
I also wonder if it's a scheme to get people through the door and then leech off them with a lifetime subscription.
Alternatives: https://electrek.co/2025/12/28/opinion-its-time-to-start-rec...
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 $10k, though I did the work myself (which would probably hae been another 3-5k if I could have found someone to do it.
Yo. If you can find an electrician to stop by my house and turn a light switch off for less than 1000$, 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.
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...
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.
I guess if you want to dabble with installing battery packs with inverters, that's not your typical bachelor of arts who is trying to do so.
Where I am at (rural CO), as long as it can be inspected and meets code, the county is fine- you don't need a blessing. Septic is different (that's a $175 certificate, though). But for electrical all you have to do is meet codes, which isn't really super hard.
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.
In 2025 it was $1,100 to have an EVSE put in, including permit fees.
I'm in Pennsylvania.
Working with my township to get a permit / inspection was horrible -- they dragged their feet for months!
I have to believe that I am one of a few people in my township who have done this the "right way".
They said it was city code causing their problem.
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...
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.
Like I said, they basically are not sold to scale like a normal household uses electricity.
EDIT: What the heck is in-rush and backfeed? Are you talking about AC input to charge the batteries? The 18k is 50A @ 240VAC (12kW) fyi. Also, why does the charge rate even matter there? For the AC output its also 12 kW...the family is average 48 kWh days, which is 2 kW hourly average...
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).
These are not terms commonly used in the industry, thanks for the clarification.
> Lots of appliances in your home have a large inrush, much larger than the breaker they're on.
And inverters are designed to compensate for short term surges too fyi. The 18k provides 65A for a few seconds as an example.
> 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?
Because you can't and don't need to...you should be asking the author of the original post, because they do what pretty much every other grid tied system which is that you pass through the power from the grid.
> Backfeed is what the inverter can push out from the battery to the home.
https://www.wartsila.com/encyclopedia/term/backfeeding huh?
> 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.
1. The 18k can push 50A on each leg and most residential are sized at 150a or 200A, which are ridiculously oversized, so at most, even with two EVs and a 4 ton AC running in Texas, I max out at 150A. I can put 3 18k's in parallel if I really want to and its STILL cheaper than a powerwall battery/inverter combo.
2. There is no reason to have a "pipe" so large that it only is used for less than 5% of the overall runtime. This is why the powerwall setup doesnt make any sense.
It's such an industry term that it's literally a named feature on multimeters.
>The 18k provides 65A for a few seconds as an example.
Yes, you'll see I gave you that spec in the opening comment. It's not a good spec for a whole home hybrid inverter.
>the 18k can push 50A on each leg and most residential are sized at 150a or 200A
That's not how you read a spec sheet for 240v device. A home service is 200 amp, at 240v. That's 48kw potential. 12k is 12k regardless of whether that's (120v * 50a) + (120v * 50a) or (240v * 50a). The legs aren't cumulative. You're implying the standing load capacity is somehow higher than its inrush capacity. It would need to be a 24kw (on the ac side, all of the janky chinese rebrand inverters all list their DC input to try to make themselves seem bigger) inverter to do what you're implying.
(50a * 120v) + (50a * 120v) = 12kw
A small home with a smaller 150 amp service is (150a * 240v), 36kw.
Edit: screw it, I'll address this as well -
>There is no reason to have a "pipe" so large that it only is used for less than 5% of the overall runtime. This is why the powerwall setup doesnt make any sense.
There sure is! The whole point is to offset usage. 50 amp standing load capacity means you can only ever offset 50 amps of usage at one time. Sure, most homes don't hold anything higher than that for long but I've seen plenty of homes hold over 20kw for a bit if they have pool pumps, well pumps, pool heaters, or any number of things going on. Any time the home draws more than 12kw instantaneously you'd be getting charged peak rates, which could be avoided with a larger standing load capacity. In addition, if you're in a municipality with a 'demand' rate you could enter in to a different billing rate any time you go over a certain amperage, meaning that ability to offset more of that in that instance, even just for an inrush, could make an even larger difference on your bill.
Look man, I run an $800 chinese inverter, and my batteries are MuRatas I harvested from decommissioned Sonnen cabinets that I rewired with chinese BMSes. The Powerwall 3 is a really good product and the pricing is great compared to comparable non-diy consumer grade products. The EG4 is not a good comparison point because it has nowhere near the spec or capability. You would need 3 EG4 18ks to have the inrush capability of a single Powerwall 3. Battery capacity (volume) is not the sole determining factor in value. This isn't even relevant but just as an aside, the EG4 isn't even a good value for the DIY scene, and has functionally the same support as rebranded drop shipped Chinese inverters.
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.
What I'm describing is using the cars DC charge port and connecting it to inverters DC battery port.
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. :-)
https://www.docanpower.com/panda-52v-942ah-48kwh-prebuilt-pa...
They are cheap and they work but they're not UL listed...so they dont go anywhere near my home.
Your point that they are overpriced still stands though.
The ROI is really attractive once you look past the overpriced kit.
(Their motor inverters are world-class, but totally different topology)
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.
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.
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?
"Another way to look at this is that the investment is returning ~9%/year."
EDIT: Two more things that will juice the return
1. Grid electricity prices will go up over those 25 years, at the very least tracking inflation.
2. Unlike bond coupon payments, the "return" from a solar installation isn't taxable. Because you're saving money, not getting paid.
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.
LiFePO4 generally degrades to 80% capacity after 10 years, that's it. Safety isn't an issue.
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.
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
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.
[edit: yes, I assume you also get batteries, I know that solar alone doesn't magically power your house.]
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.
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.
"An ATS (Automatic Transfer Switch) for solar is a crucial device that seamlessly switches your home's power between the utility grid, your solar panels/battery bank...
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.
Not for everyone, but definitely for homeowners with suitable roofs and local utilities.
> 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.
Maybe, but that power is typically generated far from where it's consumed and so you have significant transmission losses.
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 happy to pay monthly to let my electrical provider handle all that, and I'll invest my money in something with a better return.
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... :)
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.
Willing and allowed. In some countries it can only be done by certified electricians.
You can't and you will lose in court.
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.
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! :)
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.
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 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.
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...)
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.
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.
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...
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.
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.
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.
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.
> ... 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
Thing with mini-splits is you replace the entire unit so it doesn't matter.
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'
I don't see see a heat pump as complex. It's a compressor, valves and coils. The complexity are the stupid computers foisted onto us.
> I forgot this is an american centric forum and things are just made cheap/disposable because "it's cheaper'
We don't have a choice. Do you? We're all at the mercy of the manufactures.
Yay for New Zealand housing.
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 :(
thus perhaps leading to more global warming
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?
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.
Some of this extra is certainly my 6kw homelab + HVAC for that. ;)
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.
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
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.
That probably explains it.
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.
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.
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.
That's my reasoning my new build house with plenty of land. In other scenarios it might be more beneficial to go for them.
Of course the average american living in a mcmansion which wouldn't pass regulations in 1992 Poland cannot use such solutions, but really it isn't a problem of climate, you'll find passive houses from africa to norway and everywhere in between, most of them without heat pumps
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 HeatingI do think more people should consider mini-split reversible AC in the UK, but the subsidy system specifically excludes it.
https://www.gov.uk/government/news/discounts-for-families-to...
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.
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
Only using ductwork for heat recovery ventilation without also using it for heating and cooling means more complexity, instillation costs, and maintenance issues etc. Further moving air allows you to use dramatically less material for heat exchangers.
Net result higher efficiency, fewer things that can break, fewer locations something can break, and lower risks of water damage to your home etc.
I am, and I am not an american, lol.
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.
http://solarunitedneighbors.org/ | https://solarunitedneighbors.org/locations/
I’ll take free $500 all day long please.
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.
Depending on when you signed up for NEM you may have a guaranteed floor like 4¢/kWh or even much more.
You can buy a BYD HVM 22.1 kWh for 6000 euros now (£5200) vs powerwall 2 13.5kwh for 7000 euros.
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.
(Yes, yes: insert Musk related joke here.)
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?
Octopus also have more flexible battery export tariffs if you want to explore those: https://octopus.energy/smart/flux/
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!
Just looking at Havenwise (https://www.havenwise.co.uk/) and my manufacturer isn't supported.
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.
But very often these will roughly cancel each other out.
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.
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.
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.
Utilities normally consider disincentivizing this type of behavior from residential customers as one of the factors when setting their export pricing.
Pure grid cycling is also frowned on by some utilities.
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.
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.
There will at least be a lag.
https://www.energystar.gov/about/federal-tax-credits/battery...
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.
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.
> 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.
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.
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.
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!
That's why you're investigating hydro storage:
https://www.ess-news.com/2025/02/11/fortum-explores-new-pump...
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.
I consider 2 weeks of supply a bare minimum.
The article isn’t claiming this setup is universally optimal, just showing what’s possible when those pieces are combined and used deliberately.
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 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.
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
As for your other point of becoming obsolete, why care about chasing latest fads for home appliances.
I particularly love when they are telling me that my 11 year old Prius' batteries will only last 5 years before they are junk.
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.
I really need a solar solution but I feel so far out of my wheelhouse.
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?
[0] https://www.britishgas.co.uk/energy/guides/average-bill.html
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.
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.
Solar tracking trees seem to be an interesting way to get wintertime solar way up.
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.