The equivalent number of hours when solar insolation averages 1000 watts per square meter and produces the same total insolation as actual sun conditions.

The equivalent number of hours at peak sun conditions (i.e., 1 KW per sqr m) that produces the same total insolation as actual sun conditions.

The equivalent number of hours per day when solar radiation averages 1 KiloWatt per square meter. For example, 5 peak sun hours means that the energy received during total daylight hours equals the energy that would have been received had the solar radiation for 5 hours been 1 KiloWatt per square meter.