Thermostat Setbacks: How Much You Save & How to Set Them

The U.S. Department of Energy says a home can save as much as 10 percent a year on heating and cooling by changing the setpoint 7°F to 10°F for eight hours a day. Actual savings depend on the home, weather, equipment, thermostat controls, energy price, and the starting schedule. Heat pumps need more careful recovery settings so auxiliary heat does not erase the benefit.

See the Department of Energy setback guidance.

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 a fuel-fired furnace or boiler, an eight-hour setback can reduce heat loss when comfort, freeze protection, and recovery time allow it. Start with a moderate change and adjust from actual comfort and fuel use.

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

Heat-pump setback strategy depends on the controls, backup heat, and system design. A large recovery can bring on electric resistance or other backup heat. Use thermostat settings designed for the heat pump and avoid promising that every smart thermostat prevents backup heat during recovery.

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 want more consistent scheduling or the current thermostat is not controlling a heat pump correctly, A.J. LeBlanc Heating can check compatibility and configure the replacement for the system. Contact us or call 603-623-0412.

Frequently Asked Questions

How much money does a thermostat setback actually save?

DOE says a properly used setback can save up to about 10 percent annually, but it is not a guaranteed percentage. Compare actual bills and weather-normalized use rather than multiplying one degree by one fixed dollar amount.

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?

A smart thermostat can improve consistency and convenience, especially when the old thermostat is not being programmed. Payback depends on the prior schedule, equipment, installation cost, and current incentive, so do not promise one or two heating seasons.