Energy-efficient windows are judged on their performance according to a few different factors, including heat transfer, air leakage, light transference, and condensation resistance. If you're unsure whether a window is energy-efficient, look for an ENERGY STAR® label from the U.S. Environmental Protection Agency (EPA). If various products, including windows, meet energy-efficiency standards set by the federal government, the EPA issues this label to help consumers identify energy-efficient products.

Cellular shades, also known as honeycomb shades, are the most energy-efficient and insulating window treatments. Their honeycomb structure is made of soft fabric that forms layered cell pockets. These pockets trap air, creating a thermal barrier that reduces heat loss in the winter and blocks heat gain in the summer. For even greater insulation, consider double- or triple-cell varieties. Side-tracked cellular shades, which seal the edges of the window frame, can further minimize air leaks and maximize energy efficiency.

The most energy-efficient windows are double—or triple-pane windows with low-emissivity (Low-E) coatings and gas fills between the panes. These windows reduce heat transfer, prevent drafts, and help maintain a consistent indoor temperature. But if replacing windows isn’t in your budget, pairing your existing windows with insulating window treatments can still make a noticeable difference in home comfort and monthly bills. 

No, it isn’t necessary to have energy-efficient windows. However, if you care about your energy bill and making your windows more energy efficient, fixing any heat, UV, or air transfer issues is an excellent way to lower your bills and keep your house cooler in the summer and warmer in the winter.