In Oregon: The tax credit for new alternative-fuel vehicles is based on the incremental difference between the base price of the alternative-fuel vehicle (after utility incentives and/or Federal tax credits) and the base price of the gasoline-only version of the same make and model vehicle. The tax credit is 25 percent of the incremental difference or $750, whichever is less. The tax credit for vehicle conversions and charging/fueling systems is $750 or 25 percent of the cost, whichever is less. You can get a tax credit for both an alternative fuel vehicle and a charging/fueling system
Oregon Residential Alternative Fuel Vehicle or Charging Station Tax Credit Application Form
Oregon businesses can also qualify for up to 35% of the installed cost of their charging infrastructure. http://www.oregon.gov/ENERGY/CONS/BUS/BETC.shtml
FYI, Oregon’s electric vehicle credit ended after 2011. Thought you’d want to know.