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 $5k and it's still cheaper and you wouldn't need an additional inverter every time you add a battery.
There's going to be a bloodbath in that market in the next years. There are a lot of battery producers and most of them are not producing at full capacity. At the same time, manufacturing cost is dropping as well.
Some battery makers are producing batteries at a cost level of around 60$ 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.
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.
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.
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. :-)
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.
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.
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)
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.
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.
> 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.
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]
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.
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.
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.
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.
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.
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 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 :(
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.
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.
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. ;)
It's more a stress test showing that even with unusually high consumption, solar + batteries + tariff optimisation can still materially change the cost curve
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.
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.
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.
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.
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.
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.
>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.
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!
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)?
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.
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.
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.
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.
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.
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.
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?
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
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.
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.
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.
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'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:
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
They're estimating that they'll get 30 MW on average from that, but I'd estimate more like 15 MW at a solar panel efficiency just over 20%. Still, the total cost for that power should be less than for turbines, since solar is now the cheapest electricity other than hypothetical nuclear (assuming an ideal breeder or waste-consuming reactor and excluding mining/waste externalities/insurance).
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.
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.
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.
Some comments were deferred for faster rendering.
mbesto|1 month ago
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 $5k and it's still cheaper and you wouldn't need an additional inverter every time you add a battery.
jillesvangurp|1 month ago
Some battery makers are producing batteries at a cost level of around 60$ 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.
ortusdux|1 month ago
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.
toomuchtodo|1 month ago
Alternatives: https://electrek.co/2025/12/28/opinion-its-time-to-start-rec...
modeless|1 month ago
homebessguy|1 month ago
The ROI is really attractive once you look past the overpriced kit.
tzs|1 month ago
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. :-)
dns_snek|1 month ago
chris222|1 month ago
https://www.docanpower.com/panda-52v-942ah-48kwh-prebuilt-pa...
O5vYtytb|1 month ago
Your point that they are overpriced still stands though.
torginus|1 month ago
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.
microdrum|1 month ago
(Their motor inverters are world-class, but totally different topology)
nop_slide|1 month ago
KaiserPro|1 month ago
HexPhantom|1 month ago
jstsch|1 month ago
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... :)
Dylan1312|1 month ago
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.
f1shy|1 month ago
Willing and allowed. In some countries it can only be done by certified electricians.
ViewTrick1002|1 month ago
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...
j2kun|1 month ago
MisterTea|1 month ago
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.
microdrum|1 month ago
Barbing|1 month ago
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]
boringg|1 month ago
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.
pjc50|1 month ago
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.
toomuchtodo|1 month ago
vasco|1 month ago
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.
HexPhantom|1 month ago
alberth|1 month ago
systemtest|1 month ago
kccqzy|1 month ago
bz_bz_bz|1 month ago
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.
cptcobalt|1 month ago
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.
DamonHD|1 month ago
https://www.earth.org.uk/saving-electricity.html
youngtaff|1 month ago
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
GordonS|1 month ago
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 :(
bryanrasmussen|1 month ago
thus perhaps leading to more global warming
lostlogin|1 month ago
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?
Aboutplants|1 month ago
micromacrofoot|1 month ago
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.
sponaugle|1 month ago
Some of this extra is certainly my 6kw homelab + HVAC for that. ;)
louwrentius|1 month ago
That probably explains it.
HexPhantom|1 month ago
icehawk|1 month ago
lm28469|1 month ago
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.
bob1029|1 month ago
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.
ishtanbul|1 month ago
megaman821|1 month ago
HexPhantom|1 month ago
testing22321|1 month ago
I’ll take free $500 all day long please.
dlcarrier|1 month ago
systemtest|1 month ago
riku_iki|1 month ago
coryrc|1 month ago
mikaeluman|1 month ago
lm28469|1 month ago
You can buy a BYD HVM 22.1 kWh for 6000 euros now (£5200) vs powerwall 2 13.5kwh for 7000 euros.
flakeoil|1 month ago
pja|1 month ago
(Yes, yes: insert Musk related joke here.)
elAhmo|1 month ago
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.
Scott_Helme_|1 month ago
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.
icegreentea2|1 month ago
Utilities normally consider disincentivizing this type of behavior from residential customers as one of the factors when setting their export pricing.
cptcobalt|1 month ago
Pure grid cycling is also frowned on by some utilities.
pixl97|1 month ago
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.
domh|1 month ago
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?
webjunkie|1 month ago
Scott_Helme_|1 month ago
Octopus also have more flexible battery export tariffs if you want to explore those: https://octopus.energy/smart/flux/
dabeeeenster|1 month ago
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!
Perz1val|1 month ago
syncsynchalt|1 month ago
nasmorn|1 month ago
malchow|1 month ago
https://enphase.com/ev-chargers/bidirectional
malshe|1 month ago
antisthenes|1 month ago
But very often these will roughly cancel each other out.
sounds|1 month ago
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.
willis936|1 month ago
toomuchtodo|1 month ago
https://www.energystar.gov/about/federal-tax-credits/battery...
pier25|1 month ago
coryrc|1 month ago
lysace|1 month ago
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.
pjc50|1 month ago
KaiserPro|1 month ago
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.
Havoc|1 month ago
apercu|1 month ago
I really need a solar solution but I feel so far out of my wheelhouse.
toomuchtodo|1 month ago
drak0n1c|1 month ago
deadbabe|1 month ago
j45|1 month ago
Solar tracking trees seem to be an interesting way to get wintertime solar way up.
https://youtu.be/r7HwQdssbas
testing22321|1 month ago
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.
oklahomasports|1 month ago
culebron21|1 month ago
coryrc|1 month ago
HexPhantom|1 month ago
Scott_Helme_|1 month ago
The article isn’t claiming this setup is universally optimal, just showing what’s possible when those pieces are combined and used deliberately.
bstsb|1 month ago
pornel|1 month ago
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.
drnick1|1 month ago
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.
bunderbunder|1 month ago
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.
kccqzy|1 month ago
As for your other point of becoming obsolete, why care about chasing latest fads for home appliances.
IndrekR|1 month ago
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.
NoLinkToMe|1 month ago
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.
dlisboa|1 month ago
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?
GordonS|1 month ago
[0] https://www.britishgas.co.uk/energy/guides/average-bill.html
jjice|1 month ago
Scott_Helme_|1 month ago
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.
bradphipps|1 month ago
dreadsword|1 month ago
zackmorris|1 month ago
https://techcrunch.com/2026/01/12/trumps-epa-plans-to-ignore...
They're estimating that they'll get 30 MW on average from that, but I'd estimate more like 15 MW at a solar panel efficiency just over 20%. Still, the total cost for that power should be less than for turbines, since solar is now the cheapest electricity other than hypothetical nuclear (assuming an ideal breeder or waste-consuming reactor and excluding mining/waste externalities/insurance).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.
andrewkittredge|1 month ago
[deleted]
mikaeluman|1 month ago
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.
epistasis|1 month ago
> 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.
coryrc|1 month ago
That's why you're investigating hydro storage:
https://www.ess-news.com/2025/02/11/fortum-explores-new-pump...
ImPostingOnHN|1 month ago