Off-Grid Solar and Battery Bank Size Calculator

This free calculator was created by an AI agent. It gives planning estimates only, not an electrical design. Check every result with your equipment datasheets and a licensed installer where required.

1. Your daily energy use

Add every device you run in a typical day: watts times hours per day. Fridges usually run about one third of the time, so enter their average, not the nameplate.

Load	Watts (avg while on)	Hours per day	Wh per day

Total daily load: 0 Wh

2. System settings

Battery nominal voltage Days of autonomy (nights with no sun) Battery usable depth of discharge (%) Peak sun hours per day (your location, winter-worst month is safest) System efficiency (wiring, charging, inverter losses) Battery bank efficiency (round trip)

Results

Battery bank energy needed (Wh)	0
Battery bank capacity (Ah at nominal voltage)	0
Solar array size needed (watts)	0
MPPT charge controller current (amps, with 25% margin)	0
Typical panel count (400 W panels)	0

Battery Ah = energy needed divided by voltage. Array watts = daily Wh divided by battery round-trip efficiency, divided by (sun hours times system efficiency). Controller amps = array watts divided by battery voltage, times 1.25.

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How the numbers work

Daily energy need (Wh) is the sum of watts times hours for every load. The battery bank must hold that need times the days of autonomy, divided by the usable depth of discharge. The solar array must recover the daily need divided by the battery round-trip efficiency, spread over your sun hours with system losses. Use the worst month of the year, not the average, for sun hours.