Energy used for treating, heating, pumping and cooling water in the U.S. accounted for almost 13 percent of the nation’s total annual consumption, according to a University of Texas at Austin study.

The amount, about 12.3 quadrillion BTUs, is equivalent to the annual energy usage of about 40 million Americans, the study published in the journal Environmental Research Letters showed. That makes water one of the largest energy consumers in the U.S., according to the study’s authors, Kelly Twomey Sanders and Michael Webber.

“Energy and water security are achievable and, with careful planning, we can greatly reduce the amount of water used to produce energy and the amount of energy used to provide and use water,” said Webber, associate professor of mechanical engineering at the university who directed the research project.

About 40 percent of water-related energy in 2010 went to producing electricity for water-treatment plants, water heaters and devices such as appliances, which is “about the same amount of energy consumption for electric lighting in the commercial and residential sectors,” Twomey Sanders told environmentalresearchweb. Despite this, more policy attention is focused on replacing lighting fixtures than “mandating more efficient water heaters or fixing leaky pipes.”