Currently, those who purchase a plug-in vehicle can claim back "UP TO" $7500 in Federal taxes owed in the year they buy one. However, only the very wealthy can claim the full amount, so if you only owe $4000, you lose out on the remaining $3500.
Suggest changing the tax credit so that if you don't owe $7500 in one tax year, you can claim the remainder in subsequent years.
Under this fix, if you only owed $5000 in Federal taxes one year, you could then apply for the remaining $2500 the next year. Rich people can still claim the full amount, so they are unaffected by this change.
This way, everyone, rich and poor, can claim the full amount. Plug-ins will help reduce our reliance on oil, reduce pollution, and save people money in transportation and maintenance costs.