Nameplate capacity, also known as the rated capacity, nominal capacity, installed capacity, or maximum effect, is the intended full-load sustained output of a facility such as a power plant, a chemical plant, fuel plant, metal refinery, mine, and many others. Nameplate capacity is the number registered with authorities for classifying the power output of a power station usually expressed in megawatts (MW).
Power plants with an output consistently near their nameplate capacity have a high capacity factor.
For dispatchable power, this capacity depends on the internal technical capability of the plant to maintain output for a reasonable amount of time (for example, a day), neither momentarily nor permanently, and without considering external events such as lack of fuel or internal events such as maintenance. Actual output can be different from nameplate capacity for a number of reasons depending on equipment and circumstances.
For non-dispatchable power, particularly renewable energy, nameplate capacity refers to generation under ideal conditions. Output is generally limited by weather conditions, hydroelectric dam water levels, tidal variations and other outside forces. Equipment failures and maintenance usually contribute less to capacity factor reduction than the innate variation of the power source. In photovoltaics, capacity is rated under Standard Test Conditions usually expressed in the non-SI compliant unit watt-peak (Wp). In addition, a PV system's nameplate capacity is sometimes denoted by a subindex, for example, MWDC or MWAC, in order to clarify, whether the raw DC or already converted AC power output is referred to.
The term is connected with nameplates on electrical generators as these plates describing the model name and manufacturer usually also contain the rated output, but the rated output of a power station to the electrical grid is invariably less than the generator nameplate capacity, because the components connecting the actual generator to the "grid" also use power. Thus there is a distinction between component capacity and facility capacity.