The best thermostat setting for winter, if the goal is a lower heating bill, is the lowest temperature you're comfortable with while you're home and awake, paired with a deeper setback while you sleep or the house is empty. The U.S. Department of Energy's Energy Saver guidance has put the waking number at around 68°F to 70°F, with a lower setting while you're asleep or away. Its estimate is that you can save as much as 10% a year on heating and cooling by turning your thermostat back 7°F to 10°F for 8 hours a day from its normal setting.
For a typical Massachusetts home heated by a gas or oil furnace or a hot water boiler, that works out to something like 68°F while the household is up and about and around 60°F overnight or during the workday. Heat pumps, radiant floors and steam heat call for a gentler approach, and there's a floor you shouldn't go below when you leave for a few days in January.
Why a setback saves energy, and why recovery doesn't cancel it
Thermostat setback savings come from simple physics: a house loses heat roughly in proportion to the difference between the indoor and outdoor temperature. Say it's 20°F outside. At 68°F inside, that difference is 48 degrees. At 60°F it's 40 degrees, so every hour the house sits at 60, it's losing heat about a sixth more slowly. Your heating system only has to replace the heat that leaks out, so less heat lost means less fuel or electricity used.
The usual objection is that the furnace or boiler has to work so hard to bring the house back up in the morning that it wipes out the savings. The Department of Energy has long called that a misconception, and the physics backs it up. Recovery replaces the heat the house lost while it was cooler, and that's less than it would have lost sitting at 68°F all night. The longer the setback lasts, the more you save.
One related habit worth dropping: turning the thermostat up to 80 to warm the house faster. A single-stage furnace or boiler delivers heat at the same rate whether the target is 68 or 80; you just risk overshooting. On two-stage equipment and heat pumps it can cost more, because a big gap between the setting and the room temperature is exactly what tells the thermostat to call for high stage or backup heat.
Where the advice changes
Heat pumps
Many ducted heat pumps have electric resistance heat strips as backup, usually shown as auxiliary or "aux" heat on the thermostat. Resistance heat works, but it costs considerably more to run than the heat pump itself. A deep setback creates exactly the condition that brings it on: the house is several degrees below the setting in the morning, and the thermostat calls for every bit of heat available to close the gap.
The Department of Energy's Energy Saver guide is direct about it: don't set back a heat pump's thermostat manually if it causes the backup electric resistance heat to come on, and use a smart or programmable thermostat designed for heat pumps. Those thermostats bring the temperature back gradually, giving the compressor time to do the work, and many can keep the backup heat locked out above an outdoor temperature you choose. With that setup, a modest setback of a few degrees can still pay. Without it, the cheapest heat pump thermostat setting is usually a steady one.
Ductless mini splits usually don't have resistance backup, but the same logic applies in a softer form. Like other variable-speed heat pumps, their compressors are most efficient running slowly and steadily. Recovering from a deep setback makes them run hard, often in the coldest hours before sunrise, when they're least efficient. Small setbacks, or none, tend to work best. If you're wondering how heat pumps hold up in real New England cold, our article on whether heat pumps work in a Massachusetts winter goes deeper.
Radiant floors and other high-mass systems
Radiant floor heating, especially tubing set in a concrete slab or under thick flooring, stores a lot of heat and releases it slowly. That's what makes it so comfortable, and it's also why it responds to thermostat changes over hours rather than minutes. A deep overnight setback may not recover by breakfast, or the system ends up running flat out all morning to catch up. Radiant systems generally do best with small setbacks or a steady setting. A thermostat that learns how long your system takes to recover, and starts early, can make a moderate setback work.
Steam boilers
Plenty of older Massachusetts houses still heat with steam, and steam recovers slowly too. The boiler has to bring water to a boil and push steam through cold pipes and heavy cast-iron radiators before the rooms warm, and rooms near the boiler often heat well before the far ones. Modest setbacks with an earlier recovery time work better than big swings. Steam also needs a thermostat configured for steam, which cycles the boiler less often than a forced-air setting would. Left on a furnace setting, the thermostat can run the boiler in short bursts that never get steam to the farthest radiators.
How low to set the thermostat when you're away
An ordinary overnight or workday setback poses no risk for most homes. A winter trip is different. In a Massachusetts cold snap the real risk isn't the heating bill; it's water pipes in exterior walls, in sink cabinets on outside walls, over unheated garages and in crawl spaces. When the house cools, those are the first places to freeze.
The American Red Cross recommends leaving the heat on, set no lower than 55°F, if you'll be away during cold weather. To protect pipes, it also suggests temporarily keeping the thermostat at the same temperature day and night, since a somewhat higher heating bill costs far less than a burst pipe. That's the one case where setback advice takes a back seat: in a bitter cold snap, especially if your house has pipes that have frozen before, skip the overnight setback. If you know a particular wall or bathroom is prone to freezing, treat that room as your real limit, not the reading on the hallway thermostat.
A few other precautions help when the house will be empty for more than a day or two. Don't shut off the heat to unused rooms or zones entirely; a closed-off room on an outside wall can freeze while the rest of the house is fine. If your thermostat can send a low-temperature alert to your phone, turn it on. If you heat with oil, make sure there's enough in the tank to cover the trip. And if the house can't hold temperature even when you're home, deal with that no-heat problem before you leave, not after.
Setting up a programmable or smart thermostat properly
A programmable thermostat saves money only if its schedule matches how you live. Start the setback a little before bedtime, have the warm-up finish around the time you get up, and add a daytime setback if the house sits empty for a good part of the day. If you find yourself overriding the schedule every evening, change the schedule. Constant manual holds are where most of the savings quietly disappear.
Smart thermostats add features like learning your routine, adjusting when your phone leaves the house, and adaptive recovery, which starts heating early enough to reach your target temperature at the scheduled time instead of starting then. They're convenient, but a basic programmable thermostat with a sensible schedule saves the same energy. The settings that matter more are the ones made at installation:
- Equipment type. A gas furnace, a hot water boiler, a steam boiler and a heat pump each need different settings, including how often the system is allowed to cycle.
- Staging. Two-stage furnaces and heat pumps should be wired and configured so the low stage carries most of the load, with high stage or backup heat coming on only when it's really needed.
- Heat pump balance points. Two outdoor temperatures matter: the one below which backup heat is allowed to run and, if a furnace is the backup, the one where the system switches from heat pump to furnace. Both should be set for your equipment and energy prices, not left at factory defaults.
- Power. Most smart thermostats need a common wire (often called a C-wire) for steady power. Many older systems don't have one at the thermostat, and without it some thermostats behave erratically or drain their batteries.
Location matters as well. A thermostat on an exterior wall, near a drafty door, above a supply register or in a room that gets strong afternoon sun reads the wrong temperature and runs the whole house accordingly. If one room always ends up warmer or colder than the rest no matter where the thermostat is set, the cause is usually airflow or distribution rather than the setting; our article on one room hotter than the rest of the house covers the usual culprits.
Humidity: why 68°F can feel colder in January
Cold outdoor air holds very little moisture. When it leaks into the house and warms up, its relative humidity drops sharply, and on a frigid day indoor air can get very dry. Dry air pulls moisture off your skin faster, and that evaporation makes you feel cooler than the thermostat says. The natural response is to turn the heat up, which costs money and dries the air even more.
Adding some moisture back can make a lower setting feel comfortable. The EPA suggests keeping indoor relative humidity below 60%, ideally between 30% and 50%. In a Massachusetts deep freeze, stay toward the low end of that range: water or frost collecting on the inside of windows means the air is carrying more moisture than the house can handle, and condensation brings its own problems. An inexpensive humidity meter tells you where you stand. Sealing obvious air leaks helps on both fronts, since less cold, dry outside air gets in, and a humidifier, portable or mounted on the furnace, can cover the rest.
OniFix installs and sets up thermostats for furnaces, boilers and heat pumps, including the staging and heat pump settings that decide how much a setback really saves. If your thermostat needs replacing or a proper setup, you can book a visit.
Sources: U.S. Department of Energy, Home Upgrades; U.S. Department of Energy, Energy Saver Guide (PDF); American Red Cross, Preventing and Thawing Frozen Pipes; EPA, A Brief Guide to Mold, Moisture and Your Home.