Determine the amount you paid on electricity bills before you installed your system. If your system offsets all your electricity, once you know its cost, you can divide that by the annual bill and determine how many years it will take to pay off. If you are only offsetting part of your use, you will need to adjust the calculation accordingly. Windustry has a wind energy paper on the economics of grid-tied small wind.

Cole Gustafson, North Dakota State University
Irene Shonle, Colorado State University