A recent Oak Ridge National Laboratory (ORNL) study looked at how the expected increase in electric cars and trucks will affect the power grid.

“Some assessments of electric vehicles assume owners will charge them only at night,” says Stan Hadley of ORNL’s Cooling, Heating and Power Technologies Program. “But consumers will want to plug in when it’s convenient, not when utilities prefer. The utilities will need to create incentives.” Socalled “smart” chargers that know the price of power, demands on the system, and when the car will be needed could help owners and utilities.

ORNL researchers based the study on their own predictions of electricity demand, supply, infrastructure, prices, and emission levels. They assumed electric hybrids would command a 25% market share by 2020. Scenarios were run for 2020 and 2030 with charging times of 5 and 10 p.m., in addition to other variables.

The need for added generation might be more critical in 2030, when hybrids will make up a larger proportion of automobiles. In the worst-case scenario — if all hybrid owners charge their vehicles at 5 p.m. and use 6 kW of power — up to 160 large power plants would be needed nationwide to meet the demand. The increased demand would also reduce reserve power margins in particular regions.

The best-case scenario occurs if vehicles are plugged in after 10 p.m. Based on demand projections, anywhere from zero to eight additional power plants might be needed.