Megawatt is the standard term of measurement for bulk electricity. One megawatt is 1 million watts. One million watts delivered continuously 24 hours a day for a year (8,760 hours) is called an average megawatt.
The distinction between megawatts and average megawatts is important. The total possible output of a generating plant is expressed in megawatts. This is called the plant’s generating capacity. It’s like a horsepower rating – how much a generating plant is designed to produce at full load. The maximum amount of power a generating plant is capable of producing over the course of an average year is called its generating capability or average annual energy, expressed in average megawatts.
Northwest capacity and energy for the various types of generation that make up the regional power supply are shown in pie charts on the Power Supply page of the Council’s website.
The difference between capacity – megawatts – and energy – average megawatts -- can be dramatic. For example, the capacity of Grand Coulee Dam, the largest in the Columbia River Basin and one of the largest in the world, is 6,595 megawatts but its average annual energy is 2,732 average megawatts.
As of 2017, the average residential electricity customer in the Northwest uses about 11 megawatt-hours per year. At 11 megawatt-hours per year per average household, on a regional basis, one average megawatt is enough to power 796.36 Northwest homes for a year. To use Grand Coulee Dam again as an example, its average annual energy would be enough to power 2,175,655 homes (if it only powered homes).
That’s a regional average. Electricity use varies from customer to customer and utility to utility. For example, all-electric homes consume more electricity than homes that use natural gas for furnaces, ovens, and water heaters.