Enter values
Formula and methodology
Estimated daily kWh = panel watts × count / 1,000 × peak sun hours × (1 − loss fraction). Monthly uses 30.4375 days; annual uses 365 days.
How to use the result
Check that each input uses the intended unit, then compare the displayed result with the assumptions above. Recalculate when the source values or operating conditions change. Do not use an estimate as a substitute for equipment documentation or professional review where safety depends on the result.
Reviewed sources
- PVWatts Calculator — National Renewable Energy Laboratory; reviewed September 1, 2026.
- Department of Energy Style Guide: kilowatt and kilowatt-hour — U.S. Department of Energy; reviewed September 1, 2026.
Method reviewed September 1, 2026. Scheduled review by 2028-08-31.