Plug-In Vehicles May Lead To More Power Plants

New study says planning is needed to avoid raising electricity demand

Jeff Johnson

The time of day when plug-in electric cars are charged will determine the impact they will have on the national power grid, says a new study by Oak Ridge National Laboratory (ORNL).

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The Department of Energy lab study assumes that by 2025, one-quarter of U.S. cars will run on a combination of electric and liquid fuels and will require plug-in charging. If all cars are charged at 5 PM, when electricity demand is high, some 160 large power plants will be needed nationwide to supply the extra electricity, according to the study. However, it says, if the charging is done after 10 PM, when demand is minimal, as few as eight—or possibly no—new power generation facilities will be needed, depending on the availability of regional electricity.

The study comes at a time when several automakers are exploring plug-in electric vehicles. Earlier studies, including one by Pacific Northwest National Laboratory, found that off-peak, idle capacity at existing electric utilities could provide enough power to fuel 84% of the U.S.'s 220 million cars if all of them were shifted to hybrid plug-in electric vehicles (C&EN, Dec. 18, 2006, page 40).

"That assumption doesn't necessarily take into account human nature," says ORNL's Stan Hadley, who led the study. "Consumers' inclination will be to plug in when convenient, rather than when utilities would prefer.

"Utilities will need to create incentives to encourage people to wait," Hadley continues. "There are also technologies such as ‘smart' chargers that know the price of power, the demands on the system, and the time when the car will be needed next to optimize charging for both the owner and the utility. That can help too," he adds.