Why Window Efficiency Matters

Windows are a significant source of heat loss in many homes. Upgrading to more efficient panes can reduce drafts and energy bills. This calculator provides a simple way to approximate how much energy you might save by installing new windows.

The Heat Loss Formula

Annual heat loss through windows can be approximated using:

where $U$ is the window’s U-factor, $A$ is area, and $\mathrm{HD}$ is heating degree days. Lower U-factors indicate better insulation.

Calculating Savings

The difference in heat loss between old and new windows, multiplied by a typical energy cost per BTU, gives the approximate savings. For simplicity this tool outputs the BTU difference. You can convert to dollars using your local energy rates.

Use the result to compare quotes from window installers or to decide which windows to replace first. Though simplified, this calculation demonstrates the energy benefits of high-performance glazing.