The Internet is full of bad information. For those looking to save money on their energy bills, it's hard to tell what information is legitimate and what's just someone's guess (or gym teacher's advice or whatever). Here's some bad advice we see often about thermostat setbacks (i.e., turning down your thermostat by 8 degrees for at least 8 hours, typically before going to bed and before leaving for work.): "Thermostat setbacks during the winter won't save you money. Any energy you saved when the thermostat was turned down will be lost because of the amount of fuel the furnace needed to get your home back to a comfortable level." Well, that's wrong. Setbacks certainly do save you money. We'll briefly discuss why.
One crucial heating factor forgotten It's true that your furnace will need to run longer to get your home back to its regular comfortable temperature. However, that does not mean there won't be any savings from the setback. Your furnace will run less often, and therefore cost you less money, when you set your thermostat at a lower temperature. Why? Because your home's rate of heat loss decreases at lower temperatures. (Here's a simple explanation of the rate of heat transfer.) Energy.gov explains:
"[A]s soon as your house drops below its normal temperature, it will lose energy to the surrounding environment more slowly. The lower the interior temperature, the slower the heat loss. So, the longer your house remains at the lower temperature, the more energy you save, because your house has lost less energy than it would have at the higher temperature."
For example, leaving your home at 64 degrees when you're away from home for 8 hours will save you more money than if you left it on 72 degrees because at 64 degrees your home is losing less heat than it would have at 72 degrees and therefore the furnace runs less often. Several studies have shown that there are savings from thermostat setbacks. The Canadian Centre for Housing Technology found that, "thermostat setback has significant potential as an effective and inexpensive energy-saving method, even in an energy-efficient house." Of course, the savings you get depend on how cold it really gets. The colder it is outside, the more you'll save from setbacks.
Make setbacks easy with a programmable thermostat The best time to do setbacks is when you go to bed and leave home for work. Both are 8-hour periods when heating isn't as important. But if you don't want to deal with manually setting your thermostat up and down every day and night, programmable thermostats can do it for you. They let you program setbacks and setups to happen at particular times of the day. There are different programmable thermostat models that vary on the number of schedules you can program in them: