Thermostat Setbacks

Yes, you should set back your thermostat if your home is heated by a gas, propane, or oil furnace or boiler. A thermostat setback is lowering your heating temperature (or raising your cooling temperature) when you are away or asleep, then returning to your comfortable setpoint when you need it. According to the U.S. Department of Energy, a setback saves about 1 percent for every degree per 8-hour period, up to roughly 10 percent a year from a 7 to 10 degree setback held 8 hours a day.

For a southern New Hampshire household with $1,500 in annual heating costs, an 8 to 10 degree setback for 8 hours a day is worth roughly $120 to $150 every year. For heat pump-heated homes, the answer is conditional: setbacks work only with a smart thermostat configured for heat pumps, and even then the savings are smaller. At A.J. LeBlanc Heating, here is what we tell NH customers.

The short answer by system type

• Gas, propane, or oil furnace: yes, set back. 8 to 10 degrees for 8+ hours saves meaningful money.
• Gas, propane, or oil boiler (hydronic): yes, set back. Recovery is slower than forced-air but the savings are real.
• Standard heat pump with basic thermostat: no, keep a steady setpoint. Large setbacks trigger expensive aux heat that erases the savings.
• Cold-climate heat pump with smart thermostat: modest setbacks (3 to 5 degrees) can save energy. The smart thermostat manages the recovery to avoid aux heat.
• Dual-fuel system: follow the smart thermostat's recommendations. Modern controls handle the heat pump and furnace transition automatically.

Why setbacks actually save money

A common misconception is that a furnace works harder to recover from a setback, canceling out any savings. The Department of Energy notes this is not how heat loss works:

As soon as your home drops below its normal temperature, it loses heat to the outdoors more slowly. The lower the interior temperature, the slower the heat loss. So the longer your home stays at the lower temperature, the more energy you save, because the home has lost less energy than it would have at the higher temperature. The same principle applies to raising the cooling setpoint in summer.

The recovery period uses extra fuel, but less than the home would have burned maintaining the higher temperature continuously.

Setbacks on conventional gas, propane, and oil systems

For furnaces and boilers fired by gas, propane, or oil:

• An 8 to 10 degree setback for 8 hours overnight or during a daytime work absence is the standard recommendation.
• A larger setback gives larger savings, but past about 15 degrees the recovery time becomes uncomfortable.
• A programmable thermostat that you actually use (and do not override constantly) captures the savings reliably.

How long a setback needs to last

For the savings to outweigh the recovery cost, the setback period needs to last at least 8 hours. Shorter setbacks (a couple of hours) generally do not save enough to be worth the comfort trade-off. Typical productive setback windows:

• Overnight (10 PM to 6 AM)
• Daytime when everyone is at work or school
• Extended vacation absences (do not drop below 60°F in NH winter)

Setbacks on heat pumps require different rules

This is where NH homeowners trip up most often. Heat pumps work most efficiently at a steady operating point, not in recovery mode:

• When the thermostat calls for a significant recovery (4+ degrees), the system often triggers auxiliary backup heat (electric resistance strips, or in a dual-fuel system, the furnace) to make up the difference quickly.
• Auxiliary heat costs 2 to 3 times what the heat pump costs to deliver the same heat. Triggering it for setback recovery can erase the savings the setback was supposed to produce.
• For straight heat pumps without smart thermostats, the Department of Energy recommends a moderate, steady setpoint rather than large setbacks.

Smart thermostats solve the heat pump setback problem

Modern smart thermostats designed for heat pumps (Ecobee, Nest, Honeywell Home with the right configuration) use algorithms that:

• Start the recovery early so the heat pump alone has time to bring the home back up
• Lock out auxiliary heat unless absolutely necessary
• Adjust setback strategy based on outdoor temperature

With a properly configured smart thermostat on a heat pump, modest setbacks of 3 to 5 degrees can save energy. With a basic mechanical or programmable thermostat on a heat pump, leave the setpoint steady.

NH cold-snap caution

During extreme cold stretches in New Hampshire (below zero for an extended period), avoid large setbacks even on fuel-burning systems:

• Recovery takes much longer when the outdoor temperature is very low.
• Cold interior temperatures increase the risk of frozen pipes, especially along exterior walls, in basements, and in any room that does not see frequent use.
• Keep the setpoint at 60°F or above overnight during a cold snap. The savings are not worth the pipe-burst risk.
• If you are away during a cold snap, ask a neighbor to check the home daily. Heating system failures in deep winter become emergencies fast.

Setbacks in summer cooling

For AC and heat pumps in cooling mode, raising the setpoint when you are away or asleep is straightforward:

• A higher indoor temperature slows the heat flow into the home.
• The same 1 percent per degree per 8 hours rule of thumb applies.
• Smart thermostats with occupancy sensing handle this automatically.

Schedule a smart thermostat install

If you are running a heat pump on a basic programmable thermostat (or no setback strategy at all), upgrading to a properly configured smart thermostat is one of the highest-payoff HVAC upgrades available. Contact A.J. LeBlanc Heating. Serving New Hampshire families since 1928.

Frequently Asked Questions

How much money does a thermostat setback actually save?

Roughly 1 percent for every degree of setback per 8-hour period, up to about 10 percent a year per the Department of Energy. For a NH home with $1,500 annual heating costs on a fuel-burning system, a consistent 8 to 10 degree setback held for 8 hours a day saves roughly $120 to $150 per year. The savings scale with heating fuel costs.

What is the ideal thermostat setback for a NH home?

For fuel-burning systems, 8 to 10 degrees for at least 8 hours. For heat pumps with smart thermostats, 3 to 5 degrees. Do not drop below 60°F during cold snaps regardless of system type.

Should I set back the thermostat on a heat pump?

Only with a smart thermostat that handles the recovery intelligently. Heat pumps run efficiently at steady setpoints, and large setbacks trigger expensive auxiliary heat for the recovery, which often erases the savings. With a basic mechanical or programmable thermostat, keep a steady setpoint.

What is the lowest safe thermostat setting in winter?

Do not drop below 60°F for extended periods, especially during cold snaps. Savings also diminish below the low 60s because of recovery cost and morning comfort, so 60 to 62°F is the practical floor for overnight setbacks in NH. Below that, the risk of frozen pipes (and the cost of recovering an iced-out heating system) outweighs the savings.

How long should a setback last to actually save energy?

At least 8 hours for the savings to show. Shorter setbacks (a couple of hours) typically do not save enough to be worth the comfort trade-off.

Does setback work for cooling too?

Yes. Raising the cooling setpoint when away or asleep saves energy on the same 1 percent per degree per 8 hours basis. Smart thermostats handle this automatically through occupancy sensing.

Will a smart thermostat install pay for itself?

For homes that previously did not use setbacks, yes, usually within one to two heating seasons. The combination of automated scheduling, geofencing, and occupancy sensing makes setbacks happen consistently.