Should You Turn Your Heat Down When You're Not Home?

You've probably read or heard that a heating unit has to work harder to warm up a cold house than to maintain the temperature in an already cozy space. This is what the U.S. Department of Energy likes to call a "common misconception."

The truth is that it requires more energy to keep the house at its normal temperature than to heat it back to that temperature after dialing the thermostat down. Heat naturally moves to places where it's cold. So if your heat is up, it is constantly moving from the inside of your house to the outside, even if your house is well-insulated. A home loses energy more slowly once the temperature inside drops below normal levels. The longer the house remains cold, the more energy it saves compared to the energy lost that comes when the heater is humming along at its normal temperature [sources: Department of Energy, Sierra Club].

The same principle holds for home cooling purposes. The higher the air temperature rises above typical levels inside the house, the slower it loses energy. The slower it loses energy, the easier it is to re-cool the home when you get out of bed or return at night [source: Department of Energy].

That doesn't mean you should shut the furnace or air conditioning unit off entirely before you leave your house, especially if you're going to be gone for a while. When a house gets too cold, it puts the pipes at danger of freezing. When it gets too hot, condensed air can do a number on wood floors, cabinets and other surfaces [source: Martin].

If you're looking for a sweet spot, in winter keep the thermostat at about 68 degrees F (20 degrees C) when you're home and drop it down to about 55 degrees (13 degrees C) before you go out or go to bed. The same goes for cooling costs: Keep the house warmer than normal when you're not home and try to leave the thermostat at around 78 degrees F (26 degrees C) otherwise [sources: Department of Energy, Sierra Club].

According to the U.S. Department of Energy, a family that sets back its thermostat by about 10 to 15 degrees for eight hours a day while sleeping or out of the house can save 5 to 15 percent a year on home heating costs.

Working the thermostat is an important first step to maximizing energy efficiency, but there are also a number of other things you can do to cut down on home heating and cooling costs without sacrificing too much comfort.

First, make changing temperatures easier by investing in a programmable thermostat. This technology allows users to schedule heating levels to automatically rise when they wake up or come home at the end of the day. Most of the devices also let users to store and repeat daily settings and can be changed manually when necessary [source: Department of Energy].

Programmable thermostats are less helpful – and may actually prove more costly – for people who rely on heat pumps to warm their homes. In heating mode, the pumps are most efficient when running at a constant, moderate level and scheduling various temperature changes can cancel out any potential savings [source: Department of Energy].

Next, make sure your heating and cooling systems are running efficiently to ensure that you're not wasting energy on them. That means cleaning filters and replacing them regularly, removing dirt and addressing corrosion on HVAC units. It also means checking that vents and radiators are not obstructed and that air ducts and heating pipes are properly sealed [source: Department of Energy].