February 21, 2020

Hourly electricity consumption varies throughout the day and across seasons

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The electricity consumed in a given period (often referred to as electricity load) varies throughout the year in somewhat predictable patterns. Total U.S. hourly electricity load is generally highest in the summer months when demand peaks in the afternoon as households and businesses are using air conditioning on hot days. During the winter months, hourly electricity load is less variable but peaks in both the morning and the evening. Load is generally lowest in the spring and autumn when homes and businesses have less need for space heating or cooling.

The U.S. Energy Information Administration (EIA) has been collecting near-real-time data on hourly electricity load for all of the balancing authorities in the Lower 48 states since 2015. These data are published on EIA’s U.S. Hourly Electric Grid Monitor and are also available for aggregated regions and for the continental United States.

Nearly all U.S. households use electricity in some form. In 2015, about 25% of homes nationwide used electricity for all their energy needs, including cooking, space heating, space cooling, and water heating. On a daily basis, electricity usage in a typical home follows the daily habits of its residents. The least amount of electricity is consumed at night when most people sleep. The generally constant amount of electricity demand is called baseload, which covers the energy used for appliances such as refrigerators and other electrical devices that run continuously.

U.S. electricity consumption is generally lower on weekends and holidays than it is during the weekdays because many commercial offices are closed and less electricity is required for lighting and computer equipment. Although some utilities’ definitions vary, the electricity industry places usage periods into two categories: on-peak hours that generally refer to the hours beginning at 7:00 a.m. until 11:00 p.m. on weekdays, and off-peak hours that are between 11:00 p.m. and 7:00 a.m. on weekdays and all day on Saturdays, Sundays, and holidays.

Electricity consumption typically cycles each day with the lowest demand occurring around 5:00 a.m. and the highest demand occurring at some point during the day (depending on the season), before falling back down during late evening hours. This variation in electricity demand follows the daily patterns of energy use by households and businesses, but it is especially dependent on weather-related factors. The overall level and shape of total U.S. electricity load varies from year to year, and typical load shapes vary across regions because of differences in weather patterns and the types of electrical equipment in use.

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During the winter, the daily cycle of U.S. total electricity load usually has a morning peak and an evening peak. Although the most common primary energy source for space heating is natural gas, about one-third of U.S. households primarily rely on electric furnaces or heat pumps. During the morning hours, electricity use rises as people turn on lights, turn up thermostats, and use hot water as they get ready for the day and as businesses and offices open. Electricity load ramps up again in the winter evenings as people return home and begin warming up their homes and cooking their meals.

Air-conditioning equipment is used in 87% of homes in the United States. During the middle of summer, air conditioning accounts for a large portion of residential and commercial electricity usage. The daily U.S. load cycle in the summer has a much wider range than in the winter because of the widespread use of air conditioning. Electricity consumption in the summer increases rapidly through the day along with temperature, reaching its maximum around 5:00 p.m. or 6:00 p.m. Average U.S. hourly electricity load peaks during the summer.

Principal contributor: Tyler Hodge