Peak Sun Hours
Peak sun hours (PSH) is a measurement of the total solar energy received at a location in a day, normalized to the equivalent number of hours of solar irradiance at the standard intensity of 1,000 W/m². A location with 5 peak sun hours receives the solar energy equivalent of 5 hours of full, unobstructed sunlight at 1,000 W/m².
Peak sun hours are not the same as daylight hours. A location might have 14 hours of daylight in summer, but only 6–7 peak sun hours when accounting for the lower solar angles at dawn and dusk and any cloud cover.
How to Use Peak Sun Hours
Peak sun hours are the key input for estimating solar PV system output:
Daily production (kWh) = System size (kW) × PSH × Performance ratio
For a 10 kW system with 5.5 PSH and a 0.80 performance ratio:
10 × 5.5 × 0.80 = 44 kWh/day
Typical US peak sun hour ranges:
- Arizona, Nevada, New Mexico: 6.0–7.5 PSH
- California, Colorado, Texas: 5.0–6.5 PSH
- Southeast US, Midwest: 4.5–5.5 PSH
- Northeast US, Pacific Northwest: 3.5–4.5 PSH
SolarScope displays peak sun hours for your project location based on NASA POWER irradiance data, providing both monthly and annual averages.