For every one degree that you lower your thermostat, Funk said you can cut heating costs by 2 percent. So if you lower your thermostat from 70 to 65 degrees F, you save about 10 percent.
Of course, Funk added, that's assuming you turn the thermostat down by five degrees all day long. If you turn it back only at night and when you're gone, the savings wouldn't be quite 10 percent. But it would still be significant. He recommends that homeowners turn down the thermostat whenever they are going to be gone for more than four hours.
According to Funk, the amount of heat conducted through walls, attics and floors is directly proportional to the difference between the temperature outside and the temperature inside. The greater the temperature difference, the more heat is conducted outside. So if you turn your thermostat back by five degrees, you reduce the temperature difference, as well as the amount of heat loss.
The only time when turning back the thermostat wouldn't pay off, he added, is if you have an air-to-air heat pump. When you turn the thermostat back up, this system could be fooled into thinking the heat pump can't keep up with heating demands, causing an electrical resistance heater to kick in. An electrical resistance heater is less efficient than the heat pump.
Although turning back the thermostat usually pays off, Funk does not recommend another typical energy-saving tactic - shutting off the register in one room and closing the door.
"The problem," he said, "is that by doing that you reduce the amount of air flow over the heat exchanger of the furnace. This reduces the efficiency of the furnace."
Funk also offers these tips to save heating costs:
1) Replace or clean furnace filters every month.
2) Close vents in crawl spaces all year-round.
3) Caulk around windows and doors.
4) Replace worn or missing door and window seals and weather-stripping.
5) Place foam gaskets behind electrical outlet gaskets.
6) Insulate attic access doors.
7) Seal leaky ducts in unconditioned spaces such as attics, crawl spaces and basements.
8) Use either mastic material or foil type duct tape—not plastic duct tape.
9) Insulate the water heater tank and pipes. If you increase the water heater jacket from an R8 to an R12 rating, there is less heat loss at "standby" times when the water heater is not being used.
10) Obtain a programmable thermostat, which can be set to automatically lower the temperature at nights or when you're gone during the day.
11) Make sure your fireplace is energy-efficient. With some fireplaces, you could lose more heat up the flue than you gain.
If you have a well-sealed, "tight" home, you have about a quarter of an air change per hour, Funk said. But if you have a "leaky" house, you might be getting one complete air change every hour. In other words, you have to re-heat an entire house of air every hour. And that can be a lot of air, depending on the size of the house.
"A 2,400-square-foot house contains about 1,400 pounds of air," Funk said. "That takes a lot of Btu's to warm up."