Thermoelectric Power Water Use

Thermoelectric power generation is one of the top two water use categories in the U.S. along with irrigation. Water is primarily used for cooling purposes and is withdrawn from a source, routed through a plant’s condenser to cool the steam used to generate electricity, and the heated water is directed to a cooling system to be cooled and reused or discharged. Some of the water is consumed via evaporation during the cooling process in the cooling system. Large amounts of water are needed for both steam generation and cooling, which is why large power-production facilities are often located near rivers, lakes, and (or) the ocean.

2020 Water Use

In calendar year 2020, about 59,889 million gallons per day (mgd) of freshwater was withdrawn for thermoelectric power generation across the lower 48 United States.

• About 3.9% of the water withdrawn was consumptive use (2,359 mgd), meaning it did not return to local waterbodies or groundwater.
• Withdrawals from surface water totaled 59,622 mgd (99.6%) and from groundwater 266 mgd (0.4%).
• The Midwest hydrologic region withdrew the most at about 21.3% (12,763 mgd), followed by Tennessee-Missouri at about 18.6% (11,154 mgd). The Pacific Northwest region used the least, with about 0.03% (17 mgd).
• Thermoelectric withdrawals are highest in July at 80,827 mgd, followed by August at 78,381 mgd. April has the lowest at 45,094 mgd.
• Thermoelectric power also withdrew about 18,740 mgd of saline water.

2020 thermoelectric water use estimates are from Galanter et al., 2023 accessed through the National Water Availability Assessment Data Companion, using the hydrologic region boundaries published here.

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Thermoelectric Power Water Use 1985-2020

From 1985 to 2015, thermoelectric withdrawals peaked in 2005 at about 199,058 Mgal/d and were about 131,148 Mgal/d in 2015 (-29% from 1985).

• In 2020, withdrawals were about 78,629 Mgal/d. 2020 values are modeled estimates, so the change from 2015 partly reflects different methods.
• Groundwater supplied about 0% of withdrawals in 1985, 0% in 2015, and 0% in 2020.

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How Turbines Generate Power

Thermoelectric power uses turbines to generate electricity. The mechanism for this relies on boiling water to generate steam that turns turbines to power the generators. The generators convert the turbine energy into electricity.

Cooling – A Primary Use

One of the main uses of water in the thermoelectric power industry is to condense the steam that was used to generate electricity so that it can be used again. The waste heat removed from the steam is transferred to the water in the condenser, which is then routed to a cooling system (recirculating) or to surface water (once-through). Broadly, there are two types of cooling systems:

• Once-through cooling refers to cooling systems that withdraw large volumes of water from surface-water sources such as rivers, lakes, and oceans, circulate the water through condensers, and then return the heated water to the surface water source. Consumption occurs when the discharged heated water forces evaporation from the surface of the waterbody.
• Recirculating cooling refers to cooling systems in which water is withdrawn from surface or groundwater sources (or uses reclaimed wastewater) and circulated through condensers, cooled using towers or ponds, and then recirculated to be used again in the same process. The most common way to cool the water is to use large cooling towers, where the warm water inside the towers is sprayed. Evaporation then cools the water, causing steam clouds to appear above the towers. This evaporation leads to less water being returned than what was withdrawn. Additional water withdrawals for a recirculating system are used to replace water lost to evaporation (consumption), blowdown, drift, and leakage. 

Estimating Thermoelectric Power Water Use

USGS estimates the amount of water that is withdrawn and consumed by thermoelectric power plants based on linked heat-and-water budgets, accounting for: power plant generation and cooling system technologies; the quantity of fuels consumed and electricity generated; environmental factors such as air temperatures, water temperatures, wind speed, and elevation; and thermodynamically plausible ranges of water use for power plants. Estimates prior to 2010 were generally based on water use reported by power plants to various reporting agencies, however physics-based models are currently used to estimate thermoelectric power withdrawals and consumptive use.  

Since 2000, estimates of withdrawals an/or consumptive use for thermoelectric-power generation have been provided by cooling-system type. Prior to 2000, estimates for withdrawals and consumptive use for thermoelectric-power generation were provided by fuel type (fossil fuel, nuclear, and geothermal). This information can be found at Accessing Water Use Data | U.S. Geological Survey.

USGS plans to continue use of models to estimate thermoelectric water use in the United States. The models will continue to be evaluated and refined, while providing estimates in a nationally consistent manner.