Base load

The base load on a grid is the minimum level of demand on an electrical grid over a span of time, for example, one week. Base load power sources are power stations which can economically generate the electrical power needed to satisfy this minimum demand. Because they have a relatively high annual contribution to the energy supply, they are designed with features to minimize fuel cost. Daily peaks in grid load are met with generating plants that may have higher fuel costs, but which operate for only a part of a day.

Baseload plant, (also baseload power plant or "base load power station") is an energy station devoted to the production of base load supply. Baseload plants are the production facilities used to meet some or all of a given region's continuous energy demand, and produce energy at a constant rate, usually at a low cost relative to other production facilities available to the system. Examples of baseload plants using nonrenewable fuels include nuclear and coal-fired plants. Baseload plants typically run at all times through the year except in the case of repairs or maintenance. These plants are often designed for relatively high efficiency, and may be combined cycle plants, but may take several days to start up and shut down.

Each baseload power plant on a grid is allotted a specific amount of the baseload power demand to handle. The base load power is determined by the load duration curve of the system. For a typical power system, the rule of thumb is that the base load power is usually 35-40% of the maximum load during the year.

Peaks or spikes in customer power demand are frequently handled by smaller and more responsive, but perhaps somewhat less efficient types of power plants called peaking power plants, often powered with gas turbines.

While historically large power grids have had base load power plant to exclusively meet the base load, there is no specific technical requirement for this to be so. The base load can equally well be met by the appropriate quantity of intermittent power sources and peaking power plant.

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