Residential Energy Credit

In 2013, A taxpayer is allowed a 10-percent nonbusiness energy property credit for the purchase of qualified energy efficiency improvements to existing homes
There is a limitation of $500 on the total amount of nonbusiness energy property credit that may be claimed. This limitation is a lifetime limitation, not an annual limitation.
This credit was to expire with respect to any property placed in service after December 31, 2011. ATRA, Sec. 401, extends the availability of the credit to property placed in service before January 1, 2014.
In 2013 are 30% tax credits on large energy installation projects that are geared towards environmental aware taxpayers. They include geothermal heat pumps (no upper limit, both principal residences & second homes apply). Solar energy systems (no upper limit, both principal residences & second homes apply). Small wind turbines (no upper limit, both principal residences & second homes apply). Fuel cells (up to $500 per .5 kW of power capacity and for Principal residences only).

No.You may be able to take the credits if you made energy saving improvements to your Home located in the United States in the current year. A home is where you lived in the current year and can include a house, houseboat, mobile home, cooperative apartment, condominium, and a manufactured home that conforms to Federal Manufactured Home Construction and Safety Standards. Your main home is generally the home where you live most of the time. A temporary absence due to special circumstances, such as illness, education, business, military service, or vacation, will not change your main home.

If you cannot use all of the credit because of the tax liability limit you can carry the unused portion of the credit to the following year. File form 5695 even if you cannot use any of your credit in the current year.