A lot of the cool air your a/c blasts into your home in the summer winds up outdoors because your windows let it escape.
If you live in an older home, it probably has single-pane windows. In fact, most U.S. homes do, and those windows also are letting the heat in during the summertime, forcing your air conditioner to work overtime.
If you want to replace your windows, get double-pane models, and keep R-value top of mind. The R-value is a measure of how much heat can get through the window in an hour. Windows with a high R-value allow less heat to enter your home. The greater the R-value, the greater your energy savings will be.
And look for the Energy Star label, which means the window meets strict energy-efficiency standards. If you are building a new home, installing energy-efficient windows might save you money by allowing you to purchase a smaller heater or air conditioner.