How many amp-hours does your off-grid system need?
Pick your loads, choose how many cloudy days you want covered, and pick a chemistry. The calculator runs the math we use to size battery banks for the kits we audit. The assumptions are visible — open “Show the math” under the result.
Start from a preset
Pick your loads
Lighting
Electronics
Refrigeration
Climate
Appliances
Sizing parameters
Result
Pick at least one appliance to size your battery bank.
How this works
Daily Wh is the sum of every selected appliance multiplied by hours of use per day and quantity. AC appliances (anything plugged into a 120V outlet) get scaled up by inverter losses — we use 90% efficiency, which is typical of modern pure-sine-wave inverters.
Usable depth-of-discharge (DoD)matters because batteries shouldn’t be drawn to zero. LiFePO4 tolerates 80% DoD without significantly shortening lifespan; lead-acid is conservatively rated at 50% DoD. So the same nameplate Ah delivers very different real-world capacity.
Autonomy days is the buffer for cloudy weather. The math is: (daily AC-adjusted Wh × autonomy days) ÷ usable DoD = required nameplate Wh. Then divide by system voltage to get Ah.
This is a sizing tool, not a sales tool. Match the number against our tracked kits to find a real product that hits the spec.