Peaking power

Peaking power plants, also known as peaker plants, and occasionally just "peakers," are power plants that generally run only when there is a high demand, known as peak demand, for electricity. Because they supply power only occasionally, the power supplied commands a much higher price per kilowatt hour than base load power. Peak load power plants are dispatched in combination with base load power plants, which supply a dependable and consistent amount of electricity, meeting the minimum demand.

Peak hours usually occur in the morning or late afternoon/evening depending on location. In temperate climates peak hours often occur when household appliances are heavily used in the evening after work hours. In hot climates the peak is usually late afternoon when air conditioning load is high, during this time many workplaces are still open and consuming power. In cold climates the peak is in the morning when space heating and industry are both starting up.

A peaker plant may operate many hours a day, or it may operate only a few hours per year, depending on the condition of the region's electrical grid. Because of the cost of building an efficient power plant, if a peaker plant is only going to be run for a short or highly variable time it does not make economic sense to make it as efficient as a base load power plant. In addition, the equipment and fuels used in base load plants are often unsuitable for use in peaker plants because the fluctuating conditions would severely strain the equipment. For these reasons, nuclear, geothermal, waste-to-energy, coal and biomass are rarely, if ever, operated as peaker plants.

For countries that are trending away from coal fired baseload plants and towards intermittent energy sources such as wind and solar, there is a corresponding increase in the need for peaking or load following power plants and the use of a grid intertie.

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