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Phrase of the Day: Peak Load

August 27, 2015 by Alexandra Aznar

Peak load, also known as peak demand, refers to the maximum demand for energy during a given time period, typically a day (EIA, 2015). The figure below shows a fairly typical 24-hour load curve for summer and winter months at one location. The demand for energy in the summer rises throughout the day and peaks in the late afternoon. The pattern is similar, but not as pronounced in the winter due to differences between heating and cooling needs.

Understanding this concept is important because solar is a useful energy resource for meeting peak load, since high solar energy production generally overlaps with peak load. In other words, during the afternoon when the sun is most intense and solar energy production is high (especially during summer months), electricity customers are using the most energy, often for air conditioning. Utilities may charge more for electricity required to meet this peak load, as they need to buy or produce extra electricity to meet the extra demand.

Two graphs, one with red hues showing electricity demand in the summer, and one with blue hues showing winter electricity demands.

Peak electricity load for a typical summer and winter day. Source