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Solar recharge calculator

Panel watts and hours of sun in. Out come the energy a day and the hours of sun to refill a power station, with 75% of the panel rating counted.

Updated

Pick one to cap the panels at its solar input limit and to see the time to refill.

watts

The rated watts of all panels together, from their labels.

hours

Hours of full strength sun, not hours of daylight. The default is 4. Winter, cloud and shade bring it down.

Results

600 Wh a day from 200 W of panels in 4 hours of sun.

What the panels give

600Wh

a day

200 W × 4 h × 0.75 = 600 Wh

Why 75% of the panel rating

A panel's rating is measured in lab conditions. On a roof or a camp table, heat, the sun's angle, dust, cable losses and the charge controller take a share. We count 75% of the rated watts for every hour of peak sun, so a 200 W panel gives 150 W. A station also never takes more than its own solar input limit, whatever the panels could give.

Use these panels in the runtime calculator

What the numbers mean

The energy a day is the panel watts, capped at the station's solar input limit, times the peak sun hours, times 0.75. The hours to refill divide the station's rated capacity by the watts that reach it after the same 0.75.

Both figures assume a battery that starts empty and panels in full sun for the hours you enter. The runtime calculator uses the same numbers when you add solar under "Assumptions and solar".