In 2005, the U.S. used about 201,000 million gallons of water per day (Mgal/d) to produce electricity (not counting hydroelectric plants).  Producing electrical power is one of the largest uses of water in the United States, and the water is used primarily to cool the power generating equipment. Power plants are usually located near water sources because of the need for water (from the USGS Water Science School). 

In Illinois, thermoelectric power generation accounted for more than 80% of the total withdrawals of water in Illinois in 2005. Illinois used more fresh water for that purpose in 2005 than any other state (from Estimated Use of Water in the United States in 2005, USGS Circular 1344, see Table 2A).