Capacity Factor

Capacity factor compares how much energy a power system actually delivered over a period with how much it would have delivered if it had run at full rated power every hour of that period. The denominator, P_rated × t, is the maximum possible energy over that time in ideal conditions, so taking the ratio tells you how fully the asset was utilized. This is especially useful for sources like wind and solar, whose output varies with weather and daylight, so their average production is usually well below nameplate capacity.

Use this when evaluating the performance of renewable generators such as wind turbines, solar farms, hydro plants, or biomass units over a day, month, or year. It is also useful for comparing different sites or technologies on a common basis, even if their rated powers are different.

• Using kW for power and MWh for energy without converting units first
• Dividing by the rated power alone instead of rated power multiplied by time
• Confusing capacity factor with efficiency; capacity factor measures utilization over time, not energy conversion losses