How many gallons of water does it take you to drive to work every day? That's the question Michael Webber, an assistant professor at the University of Texas at Austin, would like people to start asking themselves. The answer, of course, depends on how you get there.
A 30-mile commute in a gasoline-powered car would require the withdrawal of 18.9 gallons of water, according to in the journal Environmental Science & Technology. The same commute in a plug-in hybrid electric vehicle (PHEV), meanwhile, would take a whopping 318 gallons. All told, electric miles necessitate threefold the water consumption and 17 times the water withdrawal of gasoline miles.
But wait, aren't PHEVs the environmentally friendly choice? "If you are a plug-in hybrid owner and you have wind or solar power at your house, then you can feel really good about your plug-in hybrid using very little water, if any," Webber told PM. "If you're a hybrid owner and are plugging your car into the standard U.S. grid, then your car is not very clean, nor is it water-free."
With the grid's current composition, electricity production requires about 136,000 million gallons of freshwater per day, accounting for over 40 percent of all daily freshwater withdrawals in the nation. That's because coal-fired and nuclear power plants that use steam to drive a turbine typically use water—vast amounts of water—to cool and condense the steam at the exhaust.
Though most of this water is returned to the source (albeit at a higher temperature), a 17-fold increase in demand would pose a real problem for water-stressed regions, making power plants more vulnerable to shut down during times of drought. Freshwater withdrawals already exceed precipitation in many areas across the country, according to a 2006 report by the Department of Energy, and groundwater levels have consequently dropped hundreds of feet.
In order to avoid having to choose between powering our cars and turning on the lights—or taking showers and driving to work—Webber concluded that Americans need to approach a plug-in vehicle culture cautiously. Upping the amount of wind and solar power in the national grid would be one way to reduce the impact; another would be to shift to air-cooled power plants, which are less efficient, but perhaps less costly to society in the end.
One thing we don't want to do is leapfrog over hybrid-electric and into the drivers' seats of 234 million vehicles powered by irrigated feedstocks. The USDA estimates that it requires 2200 gallons of water to grow a bushel of corn, which only averages 2.7 gallons of ethanol. We could get further with an aboveground pool's worth of water by swimming in it.