If you're going to install a 95 percent efficient furnace in your primary U.S. home before the end of 2010, the federal tax credit will cover 30 percent up to $1,500 of the installation and equipment costs. In order to receive the credit, you'll need to owe money on your 2010 federal income tax returns. There are several other qualifying measures as well including air sealing, insulation, water heaters and more.

If you purchase a 96 percent efficient furnace with a variable speed motor (VSM), you may also be eligible for a $300 rebate from PG&E. Without the VSM, it would qualify for a $250 rebate. If you purchase a 95 percent efficient furnace, you'd be eligible for a $200 rebate if it had a VSM and a $150 without.