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Solar panel and battery size calculator

Panel watts, battery size and controller current for a daily load.

Try the circuit in the labBuild it on the simulator's bench and measure it.

How it is worked out

Panel watts = daily Wh ÷ (sun hours × (1 − losses)). Losses cover heat, dust, wiring, the controller and the battery's charge efficiency; 20–30 % is realistic.

Battery Wh = daily Wh × days of autonomy ÷ usable depth. Controller amps ≈ panel watts ÷ battery volts × 1.25.

Example: 600 Wh a day with 4.5 sun hours and 25 % losses needs about 180 W of panels; 1.5 days on LiFePO4 needs 1125 Wh, 47 Ah at 24 V; the controller should handle about 10 A.

Peak sun hours: in the Philippines typically 4–5.5 h, lower in the rainy season; use the worst month you need to cover.

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