What you need
Every setup does four things: make power, move it, store it, and let you use it. Here's yours.
| 6 | Solar panelsMake the power |
| 1 | InverterMoves it into the batteries, gives you outlets |
| 2 | BatteriesStore it for night and grey days |
| 1 | Wiring, fuses & mountsHold it together, keep it safe |
How much power you use
Your answers come to about 9.0 kilowatt-hours a day — the same unit on a power bill. That one number sizes everything else.
In your darkest weeks the sun doesn't quite keep up, so the batteries end each day a little lower. That's by design: backup panels stretch an outage, so the batteries last about 1.5 days or more.
In summer they're full again by 3pm, and the extra sun is yours to use.
Starting full at 6pm, the batteries run the night, drop to their lowest around 9am (5%), then the panels make about 5.2 kWh a day in your darkest month against about 9.0 kWh used. After two days they sit at 17%.
Go deeper: the math
Your answers add up to about 9.0 kWh a day.
Massachusetts gets about 2.7 hours of strong sun a day in December, its darkest month (NASA data). Wires and heat lose about a quarter, plus 10% for luck.
4.5 ÷ 2.7 ÷ 0.77 × 1.1 = 2.4 kW → 6 × 410 WTo cover your outage, you need about 9.0 kWh stored. Each battery holds about 4.6 kWh you can actually use.
9.0 × 1.0 = 9.0 kWh → 2 batteriesWant to plug in your own numbers? Use the sizing calculator. More: How much power do you use? · Peak sun hours · kW vs kWh
Panels make it
6 panels. Sized for your darkest month, so you have enough all year — plenty, not barely.
Panels are all about the same now. Buy the best price from a real distributor, often by the pallet2. Used panels are fine for ground mounts.
The catchEach one is about the size of a door. Plan on two people to mount them.
Recommended. In your darkest month it takes 5+ days to refill — more panels or a generator helps.
Go deeper: panels
- Fewer, bigger panels are easier to mount than lots of small ones — same power.
- Face them south. Hot panels make a bit less power, so leave airflow behind them.
- They last 30+ years and lose about half a percent a year. Wipe them once a year if you feel like it.
More: What is a solar array? · Fewer big panels or more small?
Batteries store it
2 batteries. They save the day's sun for later — enough to run your normal life for about 25 hours with no sun at all.
The home battery most DIY setups run24. Stacks neatly in a rack, lasts well over ten years, and talks to the inverter out of the box.
The catchHeavy — plan on two people per battery — and they can't charge below freezing, so keep them indoors.
Buy once, set for good: double batteries (they last far longer used gently), plus a spare inverter and panels.
Go deeper: batteries
- Lithium iron phosphate (LiFePO4) only. You can use nearly all of it; lead-acid you can only use half.
- Add more later on the same rack as life grows.
- Keep them indoors or somewhere that doesn't freeze.
- Lifetime kit: batteries that only ever work half as hard last far longer, so doubling up is the way to buy for decades. Spares on a shelf aren't — they age and get cheaper every year.
More: Server-rack batteries, explained · LiFePO4 vs lead-acid · Batteries in cold weather
The inverter move it & use it
At house size, the charge controller and inverter come together in one box. It moves panel power into the batteries and gives you normal outlets. Works with your grid day to day, then takes over by itself when the power goes out.
Putting it together
Most people do some of it themselves and hire help for the rest. Pick what sounds like you.
What it costs, and what it saves
You pay once. After that, the power is yours.
| One-time cost | $9,500 – $12,000, parts and wiring |
|---|---|
| Off your power bill | about $450 a year at today's rates |
| Pays for itself | in about 22 years |
Over a lifetime
- TodayBuy it once
- ~15 yrsSwap the batteries — about $2,300 at today's prices.
- 30+ yrsPanels still making power
- Any timeAdd batteries as life grows
Prices move. This is a ballpark from the last price check. More: What off-grid solar costs
See it running
Real setups like this one. Watch how it's going for them.
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1
Down to Earth Homesteaders YouTube · Family homestead: about 3.6 kW of panels, 8 Battle Born batteries, VictronWatch
Years of real family use. Today, rack batteries are the better call for a home this size. (Affiliate links)
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2
Country Living Experience YouTube · A full-size homestead house: 20 panels, 3 EG4 rack batteries, 2 Growatt invertersWatch
Almost exactly the home setup in this guide. (Signature Solar referral links and a coupon code)
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3
DavidPoz YouTube · A year off grid on 6 rack batteries (Gyll, now sold as EG4) and 2 Growatt invertersWatch
His verdict after a year: "They have been working great." Same batteries, twice the storage: the rack grows with you. (Affiliate links; some videos are Signature Solar paid promotions)
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4
Will Prowse YouTube · DIY Solar Forum · Independent teardowns and tests of batteries, inverters and power stationsWatch
Tests the gear so you don't have to. (Earns from affiliate links too)
Running something like this yourself? Share your setup and help the next person.
Parts checklist
Everything in one list. Tick things off as you get them.
Never type this again. A free account keeps this setup, your location and these checkmarks on any device.
Some links are affiliate links.
Questions people ask
How many batteries do I need for a home backup?
For typical home backup use (about 9.0 kWh a day) with about a day, about 2 EG4 LifePower4 batteries. Tap the questions above to size it for your exact life and location.
How many solar panels do I need?
About 6 × 410 W panels (2.5 kW), sized for your darkest month rather than the average, so winter doesn't catch you out.
How much does it cost?
Roughly $9,500 – $12,000 one time for parts and wiring. After that the power is free.
Make this guide better
Know a cheaper, better way? Every idea gets read, the good ones get tested, and when one changes a pick, you get the credit.
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