Definition: Capacity factor
From Open Energy Information
The ratio of actual energy produced by an energy generating unit or system in a given period, to the hypothetical maximum possible (i.e. energy produced from continuous operation at full rated power)
- The net capacity factor is the unitless ratio of an actual electrical energy output over a given period of time to the maximum possible electrical energy output over that period. The capacity factor is defined for any electricity producing installation, such as a fuel consuming power plant or one using renewable energy, such as wind or the sun. The average capacity factor can also be defined for any class of such installations, and can be used to compare different types of electricity production. The maximum possible energy output of a given installation assumes its continuous operation at full nameplate capacity over the relevant period. The actual energy output during that period and the capacity factor vary greatly depending on a range of factors. The capacity factor can never exceed the availability factor, or uptime during the period. Uptime can be reduced due to, for example, reliability issues and maintenance, scheduled or unscheduled. Other factors include the design of the installation, its location, the type of electricity production and with it either the fuel being used or, for renewable energy, the local weather conditions. Additionally, the capacity factor can be subject to regulatory constraints and market forces, potentially affecting both its fuel purchase and its electricity sale. The capacity factor is often computed over a timescale of a year, averaging out most temporal fluctuations. However, it can be also computed for a month to gain insight into seasonal fluctuations. Alternatively, it be computed over the lifetime of the power source, both while operational and after decommissioning.