As the furnace is one of the biggest energy consumers in modern homes, its efficiency level directly affects your bottom line. So, as winter gets underway, be sure to scrutinize your monthly energy bills. If you’re paying much more than last year—and the rates haven't risen—the explanation may be that "your furnace needs attention," Kenyon says. Newer, well-maintained appliances tend to perform at peak efficiency level; older ones usually don't. Depending on circumstances, Kenyon says, “repair may be able to deliver an efficiency boost." But if not, he says, “the increase in operating costs may be reason enough to install a new unit."