Tax Credits for Plug-Ins Favor Big Batteries

The larger the battery pack, the bigger the subsidy. The law calls for a base credit of $2,500 for plug-in hybrid purchases, which increases by $417 for each kilowatt-hour of battery capacity over four kilowatt-hours, to a maximum of $7,500. So the Chevrolet Volt, scheduled to go on sale in late 2010 with a 16 kilowatt-hour pack, would presumably qualify for the full subsidy. Other vehicles with smaller packs, including a possible plug-in version of the Toyota Prius, would get a smaller credit even if the car had superior performance and range.