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.

Replacing a window frame will improve your home’s energy efficiency if the old frame is cracked or damaged in a way that allows unconditioned air from the outside into your living space or if you upgrade to a more energy-efficient window frame material. Aluminum is the least energy-efficient window frame material, followed by vinyl and wood. Fiberglass and composite frames are the most energy-efficient.

If you have central air conditioning, it’s fine to run your AC all day if that’s what you want—as long as the AC unit is in good condition. But if your AC runs constantly when you don’t want it to, there may be a problem with your system (like the ones we’ve mentioned above). Window AC units and wall air conditioners aren’t as powerful as central AC, so you should only run those kinds of air conditioners for eight to 12 hours at a time.

If you want a new boiler that’s going to help lower your fuel bills, you should buy one that has a high energy-efficiency rating. For example, a boiler that is rated “A” uses at least 90% of the energy created by the boiler. And in order to enjoy the best performance, it’s important to have it installed properly by a highly-rated tech.