which determine the durations the plant is planned to produce electricity. A solar photovoltaic plant is not planned to operate in the dark of a night, hence unplanned maintenance occurring whilst the sun is set does not impact the availability factor.

Periods of generation where only partial generation of planned capacity occurs may or may not be deducted from the availability factor. An example of partial generation is a power plant with four installed turbines planned to be concurrently operational, but one of those turbines subsequently