The capacity factor is the ratio of the system's electrical output in the first year of operation to the system's electrical output if it operated at its nameplate capacity for every hour of the year.

Capacity Factor = Annual Energy (kWhac/yr) / ( System Capacity (kWdc or kWac) * 8760 (h/yr) )

Where Annual Energy is the total annual electric generation in the first year of operation, and System Capacity is the system's nameplate capacity (see table below), and 8760 is the number of hours in one year.

For PV systems, the capacity factor is either an AC-to-DC value and labeled as DC Capacity Factor, or an AC-to-AC value labeled as AC Capacity Factor. For other systems, the capacity is an AC-to-AC value.

For systems with batteries, Net Annual Energy

The system nameplate capacity depends on the technology being modeled. SAM converts the capacity value to the appropriate units (MW, kW, or W) before using it to calculate metrics such as the capacity factor, or the value of costs and incentives expressed in $/W. For the photovoltaic models, the capacity is a DC power rating, and for the others it is an AC power rating. For the Solar Water Heating Model, the capacity is a thermal rating, while for the others it is an electric rating.

Note. For the Detailed Photovoltaic and PVWatts models, SAM calculates both a DC capacity factor and an AC capacity factor. The table below shows the value used for both the AC and DC system capacity for these calculations.

Table 9. Nameplate system capacity values for each technology.