Solar Panel Output Calculator

Direct answer

Multiply system capacity in kW by location-specific peak sun hours, then retain the share left after your loss assumption. NREL’s PVWatts tool estimates photovoltaic production from a fuller set of system and location inputs and documents inherent uncertainty; this calculator keeps only the stated scenario visible.

Variables and formula

• System capacity: the photovoltaic system’s nameplate kW capacity.
• Peak sun hours: the location-specific daily average you choose.
• System losses: a combined percentage assumption for the scenario.

Estimated daily kWh = Capacity kW × Peak sun hours × (1 − Losses ÷ 100)

Reproducible example

For 5 kW, 4.5 peak sun hours and 14% losses, 5 × 4.5 × (1 − 0.14) = 19.35 kWh per day. The simple annual estimate is 19.35 × 365 = 7,062.75 kWh.

Interpretation

The result changes directly with capacity, sunlight and losses. It does not establish a production guarantee or a financial return.

Assumptions and limitations

• Your peak-sun-hour value represents the stated site and period.
• Capacity, orientation, shading and losses fit the scenario.
• It is not a site survey, engineering design, interconnection analysis or financial projection.

Common mistakes

• Using hours of daylight instead of peak sun hours.
• Mixing a kW capacity with a monthly sun-hours figure.
• Treating the 365-day extrapolation as a location-specific production guarantee.

Assumptions

• Peak sun hours represent the selected location and period.
• The entered capacity, orientation, shading and loss assumption are appropriate for the system.
• This transparent estimate is not a site survey, engineering design, production guarantee, interconnection analysis or financial projection.

Sources and methodology

CalcMotive publishes the formula and assumptions so you can decide whether the estimate fits your use case. See our methodology standards.

• PVWatts Calculator; National Renewable Energy Laboratory; accessed Aug 17, 2026