Part of the Stimulus Bill includes a tax credit available to homeowners that make their homes more energy efficient. Replacement windows and doors are one of those energy efficient improvements. You can receive a credit of 30% of the cost up to a maximum credit of $ 1,500.00. The replacement windows must be installed by a professional contractor. There are certain energy related requirements tied to the tax credit. The windows must have a U-FACTOR rating of .30 or lower and also have a SHGC rating of .30 or lower.