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Solar panel output calculator

How much power will a portable or rooftop solar panel give you in a day?

Peak sun hours

A "peak sun hour" is an hour of full, 1,000 W/m² sunshine. A sunny summer day in much of the US, Europe or Australia gives about 4 to 6 peak sun hours; a cloudy winter day can give less than 1. Solar resource maps from national energy agencies (such as NREL in the US) give the figure for your area by month.

Losses

Real panels lose energy to heat, dust, wiring, shading and the charge controller. NREL's PVWatts calculator uses 14% total losses by default for a typical installed system; small portable kits often lose more. A panel also only makes its rating when it faces the sun squarely — tilt it towards the sun at noon (see where the sun is now).

For planning and general information. In an emergency, follow the instructions of your local authorities and call your emergency number (911, 112, 999 or 000).

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Source: arithmetic; default losses from NREL PVWatts (US National Renewable Energy Laboratory).