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I have a home in the southwest that is offgrid and runs entirely off solar. It has a 43kwh battery that covers 100% of it's needs including AC. It has a 4kw sol

I have a home in the southwest that is offgrid and runs entirely off solar. It has a 43kwh battery that covers 100% of it's needs including AC. It has a 4kw solar array. The batteries shipped to your home inclusive of all taxes and fees, UL listed, are only $5,400 today from a variety of reputable suppliers. This is obviously different than urban london but I wanted to point out just how economical this is for huge swaths of the country and how absolutely absurd some of the pricing I see on things like tesla powerwall are. Note: There are a lot of components to an installed battery system that effect pricing such as racking, wires, busbars, breakers, etc, etc. I am referring only to the enclosed battery units with BMS.

jorblumesea 1y ago
how are you able to charge 43kwh on such a small array? we have a 12 kwh setup and it recharges a 15 kwh battery in a few hours.
- duffpkg 1y ago
  In that part of southwest there are only a handful of cloudy days per year and at a relatively low latitude.
- lnsru 1y ago
  What’s the charging/discharge power of your battery? Is it AC or DC coupled?
  - duffpkg 1y ago
    My battery is 3 separate "48v" x 280ah units in parallel. There is no grid so I am not sure what you mean by coupled. The batteries output DC to inverters which output AC. It is several years old at this point, probably the better value is in "48v" x 320ah setups now. The breakers/busbars, etc are setup for max discharge of 200A but in practice I have never gotten anywhere near that.
    - lnsru 1y ago
      As electrician I install PV systems and the Chinese have nice battery+inverter combos. Inverter feeds the battery at 480V@10A DC and then the battery later delivers 3-5 kW back over the inverter. Batteries are modular and can go up to 50 kwh. 10kW rated inverter with ~10 kWp panels fully charges 10 kWh battery in couple hours and produces additional 40-50 kWh on a sunny day (southern Germany). Probably the advantage of these products is high voltage and system integration. Sadly I have no good advice for your setup.
fyrn_ 1y ago
What are these batteries?
- duffpkg 1y ago
  I did not name specifics because things are constantly changing in this market and these threads tend to live for years. Stock and prices are constantly changing but RUiXU, EG4 and EcoWorthy are widely available brands with UL listed options. Will Prowse's website has a page dedicated to code compliant batteries and there are several long lists and excel sheets on the diysolarforum.
  - mbesto 1y ago
    Eco Worthy is not UL Listed and 45 kWh of RUiXU/EG4 is $10k+. Everything you've said is pretty spot on except for 45 kWh UL-listed batteries at $5,400.
_zoltan_ 1y ago
if you could tell me where I could get UL certified 43kWh battery for $5,400 I'd be very interested.
- thechao 1y ago
  I don't know about 43kWH/5400$. But, here's the system I've been looking at: https://www.expertpower.us/products/10800w-50kwh?_pos=2&_sid=5e777028d&_ss=r https://www.expertpower.us/products/10800w-50kwh?_pos=2&_sid... That's 50KWH of battery, plus the 10.8KW of solar, inverters, etc., all for $17K. That system is microgrid (not grid following) capable; so, you can run it during a blackout. The switchover is pretty good, too, so you don't need a second backup system.
  - duffpkg 1y ago
    If I had to recommend in all in one kit, this september 2025, I would recommend an EG4 kit from Santan Solar. At brief glance they appear to be a stronger value and is from a company with a pretty strong customer service record. This is not sponsored in anyway.
  - mbesto 1y ago
    I would definitely get EG4 over Expert Power for the reasons posted by other commentators. Example kit: https://signaturesolar.com/complete-off-grid-solar-kit-eg4-6000xp-12000w-output-48v-120-240v-split-phase-12800-watts-of-solar-pv-kit-e0009/ https://signaturesolar.com/complete-off-grid-solar-kit-eg4-6... Add in a 15 kWh module and it's roughly the same price with better customer service, reliability, less parts, etc. However, I would just get an EG 18k PV, 45 kWh of EG5 batteries and 11.4 kW of solar panels from signature solar and that would cost you $18.5k
- duffpkg 1y ago
  It would be multiple batteries totaling that. Stock and prices are constantly changing but RUiXU, EG4 and EcoWorthy are widely available brands with UL listed options. Will Prowse's website has a page dedicated to code compliant batteries and there are several long lists and excel sheets on the diysolarforum.
oori 1y ago
The ratio between storage capacity and production power seems way too low, unless your daily consumption is ~10-15kWh and your batteries are over spec for harsh winter days (and then you’d need couple of sun days to recover). Are you sure about these numbers?
- duffpkg 1y ago
  In it's location the solar is very effective, the 4kw is the actual generation rather than a label rating. 100% full sun, no shade, no clouds. The array typically generates over 20kw per day. The house is pretty efficient and the weather is very nice both summer and winter. This is not an area with a harsh winter or summer. Shade and clouds of any kind, even very minor, have a HUGE effect on the production of a solar array.
  - pyrale 1y ago
    London's latitude is north of Calgary. I don't know how far south you are, but 15-20° of latitude has a significant impact on the effectiveness of solar, especially during winter.
    - duffpkg 1y ago
      Absolutely. Clouds also have a profound effect on solar output, I think much more than people realize. I am not english but my understanding is that london has a lot of clouds.
  - insane_dreamer 1y ago
    > 100% full sun, no shade, no clouds ... the weather is very nice both summer and winter Are you sure you're in the UK?
    - duffpkg 1y ago
      I am absolutely not in the UK. I am in the southwest.
more_corn 1y ago
The system I’m looking at costs twice as much for half the capacity. I’m very interested in what brand and model you speak of.
- duffpkg 1y ago
  People seem to get really mad and accusatory over these sorts of things which is why I hate posting brands and such. The information changes very frequently as to what the "best" offer is. The diysolarforum is a very good resource to find the latest information.
  - stephenitis 1y ago
    It wouldn’t be that terrible to show dated proof with receipts. Inflation has probably jacked up the prices since you bought. Dating it would help.
IncreasePosts 1y ago
If it's anything like my slice of the southwest, what works there may not work for a majority of Americans. Even when it gets very hot in the day(100+), the nights almost always drop down to 63 or less. Meaning if you have a well sealed house you can suck up cold air during the night and ride it out in the day and have very low cooling costs. Coupled with low humidity from an arid environment means you can also let the house get hotter before it feels like it is time to turn on the AC.
- duffpkg 1y ago
  This area has few days over 100 but does see relatively cool nights. It is an ideal area for this. I would say from southernmost california to southernmost texas, this basic setup is pretty workable and that includes something around 50 million americans. Regulator hurdles in some places make it impossible though. Costs are going to scale up mostly in line with the heating/cooling requirements and cloudiness of your area. My panels are ground mounted and pointed in the ideal direction. I think this contributes to their efficiency because the ground helps cool them during the hottest periods but it is a tricky thing to nail down. On a previous home I had roof mounted panels and they seemed to perform much worse, difficult to identify the exact reason though.
Izikiel43 1y ago
> The batteries shipped to your home inclusive of all taxes and fees, UL listed, are only $5,400 today from a variety of reputable suppliers. What about installation? DIY?
- duffpkg 1y ago
  That is a much more complex topic driven by the regulations where you live. Where my house is, there is more or less no regulation and you can do as you please. In a purely technical sense there is not a lot of knowhow beyond basic electrical understanding, to setup these systems. Physically speaking these 280ah or larger battery setups are VERY heavy, hundreds of pounds per unit.
  - Izikiel43 1y ago
    Do you have it in your garage or in a shed outside? I would be concerned about the fire chances.
    - duffpkg 1y ago
      It is in a utility room with some normal fire resistant features, walls are block and the electric inverters are mounted to cement board. The batteries cells themselves are in the steel cased battery boxes which help to limit potential fire risk. Very importantly these are lithium iron phosphate NOT lithium ion. There is still some fire risk with lifepo3 batteries but it is completely different than the thermal runaway possible with lithium iron.

jorblumesea 1y ago

how are you able to charge 43kwh on such a small array? we have a 12 kwh setup and it recharges a 15 kwh battery in a few hours.

duffpkg 1y ago
In that part of southwest there are only a handful of cloudy days per year and at a relatively low latitude.
lnsru 1y ago
What’s the charging/discharge power of your battery? Is it AC or DC coupled?
- duffpkg 1y ago
  My battery is 3 separate "48v" x 280ah units in parallel. There is no grid so I am not sure what you mean by coupled. The batteries output DC to inverters which output AC. It is several years old at this point, probably the better value is in "48v" x 320ah setups now. The breakers/busbars, etc are setup for max discharge of 200A but in practice I have never gotten anywhere near that.
  - lnsru 1y ago
    As electrician I install PV systems and the Chinese have nice battery+inverter combos. Inverter feeds the battery at 480V@10A DC and then the battery later delivers 3-5 kW back over the inverter. Batteries are modular and can go up to 50 kwh. 10kW rated inverter with ~10 kWp panels fully charges 10 kWh battery in couple hours and produces additional 40-50 kWh on a sunny day (southern Germany). Probably the advantage of these products is high voltage and system integration. Sadly I have no good advice for your setup.

fyrn_ 1y ago

What are these batteries?

duffpkg 1y ago
I did not name specifics because things are constantly changing in this market and these threads tend to live for years. Stock and prices are constantly changing but RUiXU, EG4 and EcoWorthy are widely available brands with UL listed options. Will Prowse's website has a page dedicated to code compliant batteries and there are several long lists and excel sheets on the diysolarforum.
- mbesto 1y ago
  Eco Worthy is not UL Listed and 45 kWh of RUiXU/EG4 is $10k+. Everything you've said is pretty spot on except for 45 kWh UL-listed batteries at $5,400.

_zoltan_ 1y ago

if you could tell me where I could get UL certified 43kWh battery for $5,400 I'd be very interested.

thechao 1y ago
I don't know about 43kWH/5400$. But, here's the system I've been looking at: https://www.expertpower.us/products/10800w-50kwh?_pos=2&_sid=5e777028d&_ss=r https://www.expertpower.us/products/10800w-50kwh?_pos=2&_sid... That's 50KWH of battery, plus the 10.8KW of solar, inverters, etc., all for $17K. That system is microgrid (not grid following) capable; so, you can run it during a blackout. The switchover is pretty good, too, so you don't need a second backup system.
- duffpkg 1y ago
  If I had to recommend in all in one kit, this september 2025, I would recommend an EG4 kit from Santan Solar. At brief glance they appear to be a stronger value and is from a company with a pretty strong customer service record. This is not sponsored in anyway.
- mbesto 1y ago
  I would definitely get EG4 over Expert Power for the reasons posted by other commentators. Example kit: https://signaturesolar.com/complete-off-grid-solar-kit-eg4-6000xp-12000w-output-48v-120-240v-split-phase-12800-watts-of-solar-pv-kit-e0009/ https://signaturesolar.com/complete-off-grid-solar-kit-eg4-6... Add in a 15 kWh module and it's roughly the same price with better customer service, reliability, less parts, etc. However, I would just get an EG 18k PV, 45 kWh of EG5 batteries and 11.4 kW of solar panels from signature solar and that would cost you $18.5k
duffpkg 1y ago
It would be multiple batteries totaling that. Stock and prices are constantly changing but RUiXU, EG4 and EcoWorthy are widely available brands with UL listed options. Will Prowse's website has a page dedicated to code compliant batteries and there are several long lists and excel sheets on the diysolarforum.

oori 1y ago

The ratio between storage capacity and production power seems way too low, unless your daily consumption is ~10-15kWh and your batteries are over spec for harsh winter days (and then you’d need couple of sun days to recover). Are you sure about these numbers?

duffpkg 1y ago
In it's location the solar is very effective, the 4kw is the actual generation rather than a label rating. 100% full sun, no shade, no clouds. The array typically generates over 20kw per day. The house is pretty efficient and the weather is very nice both summer and winter. This is not an area with a harsh winter or summer. Shade and clouds of any kind, even very minor, have a HUGE effect on the production of a solar array.
- pyrale 1y ago
  London's latitude is north of Calgary. I don't know how far south you are, but 15-20° of latitude has a significant impact on the effectiveness of solar, especially during winter.
  - duffpkg 1y ago
    Absolutely. Clouds also have a profound effect on solar output, I think much more than people realize. I am not english but my understanding is that london has a lot of clouds.
- insane_dreamer 1y ago
  > 100% full sun, no shade, no clouds ... the weather is very nice both summer and winter Are you sure you're in the UK?
  - duffpkg 1y ago
    I am absolutely not in the UK. I am in the southwest.

more_corn 1y ago

The system I’m looking at costs twice as much for half the capacity. I’m very interested in what brand and model you speak of.

duffpkg 1y ago
People seem to get really mad and accusatory over these sorts of things which is why I hate posting brands and such. The information changes very frequently as to what the "best" offer is. The diysolarforum is a very good resource to find the latest information.
- stephenitis 1y ago
  It wouldn’t be that terrible to show dated proof with receipts. Inflation has probably jacked up the prices since you bought. Dating it would help.

IncreasePosts 1y ago

If it's anything like my slice of the southwest, what works there may not work for a majority of Americans. Even when it gets very hot in the day(100+), the nights almost always drop down to 63 or less. Meaning if you have a well sealed house you can suck up cold air during the night and ride it out in the day and have very low cooling costs. Coupled with low humidity from an arid environment means you can also let the house get hotter before it feels like it is time to turn on the AC.

duffpkg 1y ago
This area has few days over 100 but does see relatively cool nights. It is an ideal area for this. I would say from southernmost california to southernmost texas, this basic setup is pretty workable and that includes something around 50 million americans. Regulator hurdles in some places make it impossible though. Costs are going to scale up mostly in line with the heating/cooling requirements and cloudiness of your area. My panels are ground mounted and pointed in the ideal direction. I think this contributes to their efficiency because the ground helps cool them during the hottest periods but it is a tricky thing to nail down. On a previous home I had roof mounted panels and they seemed to perform much worse, difficult to identify the exact reason though.

Izikiel43 1y ago

> The batteries shipped to your home inclusive of all taxes and fees, UL listed, are only $5,400 today from a variety of reputable suppliers. What about installation? DIY?

duffpkg 1y ago
That is a much more complex topic driven by the regulations where you live. Where my house is, there is more or less no regulation and you can do as you please. In a purely technical sense there is not a lot of knowhow beyond basic electrical understanding, to setup these systems. Physically speaking these 280ah or larger battery setups are VERY heavy, hundreds of pounds per unit.
- Izikiel43 1y ago
  Do you have it in your garage or in a shed outside? I would be concerned about the fire chances.
  - duffpkg 1y ago
    It is in a utility room with some normal fire resistant features, walls are block and the electric inverters are mounted to cement board. The batteries cells themselves are in the steel cased battery boxes which help to limit potential fire risk. Very importantly these are lithium iron phosphate NOT lithium ion. There is still some fire risk with lifepo3 batteries but it is completely different than the thermal runaway possible with lithium iron.