U.S. electric power sector continues water efficiency gains
As the country’s generation mix moves away from the most water-intensive sources of generation, U.S. electric power sector water withdrawals for power plant cooling remained relatively constant in 2021, increasing by just 0.3% from 2020 to 47.7 trillion gallons of water. The slight increase compares to a 2.5% rise in U.S. electricity generation in 2021.
The sector’s water-withdrawal intensity—the amount of water withdrawn per unit of electricity generated—continued to fall, declining 2.1% from 11,849 gallons per megawatthour (gal/MWh) in 2020 to 11,595 gal/MWh in 2021.
The electric power sector uses a large amount of water, mostly for cooling. Thermoelectric power plants (including natural gas, nuclear, and coal plants) boil water to create steam, which spins a turbine to generate electricity. The steam leaving the turbine must be cooled back into water to be used to generate more electricity. Plants withdraw water from nearby rivers, lakes, or oceans and pass that water through the steam leaving the turbine. That process cools and condenses the steam back into water. In 2021, 73% of the utility-scale electricity generated in the United States came from thermoelectric power plants.
The sector’s water-withdrawal intensity has largely declined over the past decade as the U.S. electricity generation mix has increasingly moved away from coal and toward natural gas and renewables.
Natural gas plants use a more energy-efficient and water-efficient technology to produce electricity than coal plants, making them less water intensive. In 2021, natural gas combined-cycle generation averaged a water-withdrawal intensity of 2,803 gal/MWh, compared with 19,185 gal/MWh for coal. Renewable generation has, on average, a very low water-withdrawal intensity. Wind and solar photovoltaic technologies, which account for most renewable generation in the United States, do not use cooling water.
The marginal uptick in water withdrawals in 2021 came as the share of coal-fired generation in the U.S. electricity mix rose for the first time since 2014. Coal-fired generation was up 16.1% in 2021 compared with 2020, rising from 773,393 gigawatthours (GWh) in 2020 to 897,999 GWh in 2021. This jump corresponded to a 769.9 billion gallon increase in water withdrawals for coal-fired generation.
Principal contributor: Paul McArdle
Tags: generation, electricity, power plants