"Upgrade Your Home
This is your last chance to claim a tax credit for making energy-efficient improvements to your principal residence. The home-energy tax credit expires at the end of this year.
It is worth 10% of the cost of new windows, doors, skylights, insulation, and heating and air conditioning systems, up to a maximum $500 credit (but no more than $200 can be allocated to new windows).
You must install the upgrades by December 31 in order to claim the credit, but you can't claim it for 2011 if you already took advantage of $500 or more of energy tax credits in previous years.
An even bigger credit is available to homeowners who install renewable-energy equipment, such as geothermal heat pumps, solar panels and small wind turbines, in their primary residence or vacation home by the end of the year. You can claim a credit for 30% of the cost, including installation, with no limit. This credit is good through 2016."
For a detailed look at all energy tax credits visit https://www.energysavers.gov/financial/70010.html