It happens in almost every home around mid-October. The first truly cold morning arrives, someone reaches for the thermostat, and the annual negotiation begins: too warm, too cold, too expensive. There is, in fact, an official answer to that argument. But it comes with a twist that most households miss, and it concerns the one room where you spend a third of your life.
The number the Department of Energy recommends
For the heating season, the U.S. Department of Energy’s Energy Saver guidance recommends setting your thermostat to 68°F while you are awake and at home, and lowering it while you are asleep or away.
The savings are concrete. Turning the thermostat back by 7 to 10 degrees for eight hours a day can cut heating costs by as much as 10% a year, a figure the agency’s recommendation is regularly cited for, including by New Hampshire’s Department of Environmental Services. The reason is simple physics: a cooler house loses heat to the outside more slowly, so the furnace burns less fuel overall, even after warming the house back up.
Why your bedroom should be cooler
At night, the logic changes, and not only for your wallet. To fall asleep, the body naturally lowers its core temperature, and a room that is too warm works against that process. According to the Sleep Foundation, most doctors recommend keeping the bedroom between 65°F and 68°F, guidance reviewed by sleep medicine physician Dr. David Rosen.
In other words, the ideal number for your living room is the top of the ideal range for your bedroom. If your home runs at 68°F all day, dropping just a few degrees overnight puts you in the sleep sweet spot, and starts the savings at the same time. Sleep is also where small changes add up, as we saw with Scarlett Johansson’s sleep supplement.
Does the rule change after 65?
Here is the twist. A study led by Amir Baniassadi, PhD, of the Hinda and Arthur Marcus Institute for Aging Research at Hebrew SeniorLife and Harvard Medical School, followed 50 older adults over nearly 11,000 nights of sleep. Published in Science of The Total Environment, it found that their sleep was most efficient when the bedroom stayed between 68°F and 77°F, and that efficiency fell by 5% to 10% as the room warmed from 77°F to 86°F.
The researchers also stressed that the ideal temperature varied a lot from one person to another. For older sleepers who often feel cold at night, 65°F may simply be too chilly, and the lower end of 68°F can be a better starting point.
How to set yours tonight
Put together, the recommendations give you a simple plan for the season:
- Daytime, when you are home: 68°F.
- Bedroom at night: 65°F to 68°F, or around 68°F if you are older or tend to wake up cold.
- Away for the day: drop it 7 to 10 degrees, and let a programmable or smart thermostat bring it back before you return.
- Adjust by one degree at a time for a few nights, rather than chasing a perfect number.
Closed windows and a warm house also mean more indoor humidity, so this is a good moment to revisit what you do in the minutes after your shower.
The bottom line
So is 68°F the magic number? During the day, yes, according to the Department of Energy. At night, your bedroom deserves its own setting, a little cooler for most adults, a little warmer for many older ones. Two numbers instead of one may be the smallest change you make this fall, and one of the few that pays you back.
