Although TMY data is commonly used for PV system simulation, the average daily solar radiation at a location in a given month is often sufficient for a basic system analysis. This data may be presented either as measured on the horizontal or measured with the measuring surface perpendicular to the solar radiation (corresponding to a PV system which tracks the sun). In either case, an additional angular dependence to account for the tilt of the module will need to be incorporated in order to determine the amount of solar radiation available to a PV module.
Peak Sun Hours
The average daily solar insolation in units of kWh/m2 per day is sometimes referred to as "peak sun hours". The term "peak sun hours" refers to the solar insolation which a particular location would receive if the sun were shining at its maximum value for a certain number of hours. Since the peak solar radiation is 1 kW/m2, the number of peak sun hours is numerically identical to the average daily solar insolation. For example, a location that receives 8 kWh/m2 per day can be said to have received 8 hours of sun per day at 1 kW/m2. Being able to calculate the peak sun hours is useful because PV modules are often rated at an input rating of 1kW/m2.