Should You Leave Your Furnace On or Off?

It’s one of the constant energy efficiency debates in the winter. Is it more efficient to turn your heat on when you’re home and off when you’re not, or leave it running at a consistent temperature all the time?

There are two opposite schools of thought on the subject. For the “turn it on and off” crowd, the reasoning boils down to simple idea that if you run your furnace less, it uses less energy. There’s no reason to heat your home when you’re not actually in it, right? Those who believe in running heat at a constant temperature disagree. Their argument is based on around the idea that the energy used to start up a system and heat a cold house is actually less efficient and cost-effective than just keeping the house warm all the time.

So, who actually has the science backing them up? According the U.S. Department of Energy, “You can save as much as 10% a year on heating and cooling by simply turning your thermostat back 7°-10°F for 8 hours a day from its normal setting.” That sounds like a decisive answer, but it’s not quite that simple.

“The percentage of savings from setback is greater for buildings in milder climates than for those in more severe climates. You can easily save energy in the winter by setting the thermostat to 68°F while you're awake and setting it lower while you're asleep or away from home.”

A little bit less clear now, right? Here in the Northeast, our winters certainly count as a “more severe” climate, where it takes more energy to re-heat a home. However, there is one key principle that highlights why you should turn your heat off during the day – heat loss.

Heat loss is the real problem with your heating bills. Every home, no matter how well insulated, leaks heat to the outside. A common misconception is that when it’s freezing cold out your house will get much colder during the day and the furnace will have to work that much harder to get to a comfortable temperature.

However, when you turn your furnace off, the temperature of the home drops to closer to the level of the outside temperature, reducing heat loss. When you run the heat all day, the heat loss stays at the same consistent level and the furnace has to constantly run to maintain the temperature. While your furnace does have to work harder to get the house back up to temperature, the heat loss from having the house be significantly warmer than the outside will actually do more harm to your energy bills than the energy used to reheat the home, even if you keep your house cooler than the 68°F figure the Department of Energy uses.

If you’re not convinced, the best solution is to simply test your home. Measure the meter on your heating source to see how much is used when you leave the furnace on and how much is used to reheat the home after it’s off. Make sure you use the same time frame, same internal temperature, and similar outdoor temperatures. In all likelihood, you’ll find that turning the heat off is the most efficient option for you.

If you’re looking for better energy efficiency, consider replacing your boiler or furnace. Modern systems are far more efficient than outdated models, and will help reduce your heating costs regardless of what temperature you like the home at. HomeServe of Long Island can help with all your heating needs. Call us today at 800-691-7002 or contact us online.