Peak sun hours
The number of hours per day that sunlight averages 1,000 W/m² of intensity — the key local input for estimating how much energy a solar array will make.
Peak sun hours condense a location's daily solar energy into an equivalent number of hours at full-strength (1,000 W/m²) sunlight. The U.S. ranges from roughly 3.5 hours a day in the cloudy Northwest to 6+ in the desert Southwest.
It's the multiplier that turns system size into output: a 1 kW array in a 5-peak-sun-hour location makes about 5 kWh a day before losses. Combine peak sun hours with array size and the performance ratio to estimate annual production.
Put it to work
See also