U.S. Energy Information Administration - EIA - Independent Statistics and Analysis
Frequently Asked Questions
What is the difference between electricity generation capacity and electricity generation?
Capacity is the maximum electric output a generator can produce under specific conditions. Nameplate capacity is determined by the generator's manufacturer and indicates the maximum output a generator can produce without exceeding design thermal limits.
Net Summer Capacity and Net Winter Capacity are typically determined by a performance test and indicate the maximum load a generator can support at the point of interconnection during the respective season. The primary factors that affect or determine the difference in capacity between summer and winter months are:
- the temperature of cooling water for thermal power plants or of the ambient air for combustion turbines
- the water flow and reservoir storage characteristics for hydropower plants
Generation is the amount of electricity a generator produces over a specific period of time. For example, a generator with 1 MegaWatt (MW) capacity that operates at that capacity consistently for one hour will produce 1 MW-hour (MWh) of electricity. If it operates at only half that capacity for one hour, it will produce 0.5 MWh of electricity. Many generators do not operate at their full capacity all the time; they may vary their output according to conditions at the power plant, fuel costs, and/or as instructed from the electric power grid operator.
Net generation is the amount of gross generation a generator produces less the electricity used to operate the plant; such uses include fuel handling, feedwater pumps, combustion air fans, cooling water pumps, pollution control equipment, and other electricity needs.
Last updated: November 16, 2012
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