Q: The federal government allows up to a $1,500 energy tax credit for homeowners for certain investments such as additional insulation or upgrading from single-pane to double- or triple-pane windows.

Q: The federal government allows up to a $1,500 energy tax credit for homeowners for certain investments such as additional insulation or upgrading from single-pane to double- or triple-pane windows. Can a homeowner take a tax credit of $1,500 for tax year 2009 and an additional credit of $1,500 for tax year 2010, or is the $1,500 the maximum allowed for both years combined?

— Jason Davis, Lilburn

A: The $1,500 federal tax credit is the maximum amount offered over a two-year period, for 2009 and 2010, according to the Energy Star program, a joint effort of the U.S. Environmental Protection Agency and the U.S. Department of Energy. Homeowners can spend up to $5,000 during the two-year period on one or more products for a principal residence they own and live in and receive 30 percent, or $1,500, as a tax credit. But if you take the $1,500 tax credit in 2009, you can’t get it again in 2010. Details about what products qualify and how to apply are available at www.energystar.gov.