REFERENCE // TOOL
Solar Panel Sizing
The panel wattage needed to put back what you spend in a day.
Find the panel wattage needed to replace a day's energy use. Pair it with the daily watt-hours from the Battery Runtime calculator.
Recommended panel size
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Break-even on a good day
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Formula
panel watts = (daily load Wh ÷ (peak sun hours × loss factor)) × oversize margin. A loss factor of ~0.7 covers the 25–30% lost to heat, dirt, wiring, and the inverter. Break-even only refills the battery on a clear day — size the battery bank for the days the sun does not show.
Source: Anern — Definitive Roadmap to Sizing Your Power System · EleCalculator solar sizing (2025).