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More or Less Electricity If plug-in hybrid electric vehicles are developed and purchased by consumers for short commuting trips, several studies indicate the vehicles would reduce owners' fuel and vehicle usage costs and cut harmful emissions in half. The studies assume that owners recharge their vehicles overnight when demand for power is low.
ORNL's Stan Hadley recently conducted a different study with the assumption that that plug-in hybrid owners more likely would plug their cars into the electric grid during the day when demand for power is high. "Even at peak power prices, electricity is still cheaper than gasoline for propelling the car," he says. Using a power plant computer model he developed and utility data from Virginia and the Carolinas, Hadley simulated the effects on the grid of a million plug-in hybrids recharged daily for 5 hours at 6 p.m. versus a million plug-in hybrids plugged in overnight starting at 11 p.m. The model indicated the plug-in hybrids feeding on peak power nudged the grid to draw additional electricity from power plants that burn natural gas instead of coal. "The region has an overall regulated limit, or cap, on emissions of sulfur oxides and nitrogen oxides (NOx). Because of sales of credits from power plants with emissions below the cap, emissions would not increase throughout the country," Hadley says. "The additional production to meet this regional demand would cost utilities more because of the rising prices of the credits. As drivers shift from gasoline to electricity, more atmospheric carbon dioxide from fossil fuel combustion may be produced because carbon emissions are not yet regulated. In the United States a cap exists for NOx emissions of power plants but not vehicles. The benefits of transitioning America's vehicles to plug-in hybrids will be lower demand for gasoline and, as a result, air that is safer to breathe."—Carolyn Krause
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