Start from a build
Your appliances
- ≈400 Wh
- ≈100 Wh
- ≈200 Wh
- ≈267 Wh
- ≈556 Wh
- ≈30 Wh
- ≈30 Wh
- ≈833 Wh
System settings
Build sheet
≈2,416 Wh/day · 2 days backup · 4h sun · see the formulas
Battery bank
600 Ah @ 12V
7.2 kWh usable · LiFePO4
Solar array
1,000 W
≈ 5 × 200W panels
Charge controller
150 A MPPT
MPPT recommended (1.25× safety factor applied)
Inverter
2,000 W
Pure sine · ~4,000 W surge
Main cable: 2/0 AWG · Fuse: ~250 A
Carries up to ~185 A. Fuse at the battery positive (ANL/Class-T). Size cable up for long runs (voltage drop).
Estimates for planning only. Off-grid electrical work must follow local code — for anything beyond a simple build, have a qualified installer review it. As an Amazon Associate and affiliate, we may earn from qualifying purchases at no extra cost to you.
How it works
List your loads
Pick appliances and set how many hours a day you run each. We total your real daily watt-hours.
Set your reality
Battery type, system voltage, sun hours and how many cloudy days of backup you want.
Get exact sizes
Battery Ah/kWh, solar watts, controller amps, inverter watts and cable gauge — with gear to match.
Common questions
How many watts of solar do I need for my van or RV? +
Add up your daily energy use in watt-hours, then divide by your location's peak sun hours and a ~0.75 system efficiency factor. A typical full-time van (fridge, lights, Starlink, laptop) needs roughly 400–800W of solar. The calculator does this automatically from your appliance list.
What size battery bank do I need for off-grid? +
Take your daily watt-hours, multiply by the days of backup you want, then divide by your battery's usable depth of discharge (80% for LiFePO4, 50% for lead-acid). Divide by system voltage for amp-hours. Most vans land around 200–400Ah at 12V.
Do I need an inverter? +
Only if you run AC (mains-voltage) appliances like a microwave, induction cooktop or laptop charger. If everything is 12V DC, you can skip the inverter. Size a pure sine inverter to cover your largest simultaneous AC load.
12V, 24V or 48V — which should I choose? +
12V suits most vans and small builds. 24V and 48V reduce current (thinner, cheaper cabling) and suit larger RVs and cabins. See our 12V vs 24V vs 48V guide.
New to off-grid power?
Start with the fundamentals, then let the calculator do the math.