How thermostat setbacks save energy
Your home loses heat in winter (and gains it in summer) in proportion to the temperature difference between inside and outside. Lowering the indoor temperature for part of the day reduces that difference, so less heat escapes and the heating system runs less. It's a myth that the furnace has to "work harder" to warm the house back up – the energy saved during the setback is larger than the energy needed to recover.
Savings ≈ 1 % per °F of setback per 8 hours (US DOE rule of thumb)
Setting the thermostat back 7 – 10 °F for 8 hours a day can save up to about 10 % a year on heating and cooling. Because savings per degree are larger in milder climates, results vary by region.
Recommended settings
| Season | At home, awake | Asleep or away |
|---|
| Winter | 68 °F (20 °C) | 60 – 64 °F (16 – 18 °C) |
| Summer | 78 °F (26 °C) | 82 – 85 °F (28 – 29 °C) |
Smart vs programmable thermostats
- Programmable: follows a fixed weekly schedule. Cheap and effective – if you program it.
- Smart / learning: uses your phone's location (geofencing), occupancy sensors and learned habits to set back automatically, with app control and energy reports.
- Remote sensors balance temperatures between rooms and reduce hot or cold spots.
- Utility programs: many utilities give rebates or bill credits for smart thermostats that join demand-response events.
Heat pumps and setbacks
Heat pumps heat most efficiently when they run steadily at low output. A large setback can make the thermostat call for electric resistance backup heat to recover quickly, wiping out the savings. Use small setbacks or a thermostat with heat-pump smart recovery that warms the house gradually.
Installation checklist
- Check compatibility with your HVAC system (single-stage, multi-stage, heat pump, boiler).
- Most smart thermostats need a common (C) wire for power – some include an adapter.
- Turn off power at the breaker before replacing the old thermostat.
- Line-voltage baseboard heaters need special line-voltage thermostats.
Frequently asked questions
How much does a smart thermostat save?
Typically around 8 – 10 % of heating and cooling costs – often $100 – $200 a year for an average US home.
Is it cheaper to leave the heat on all day?
No. Lowering the temperature while you're asleep or away saves energy in almost every home.
What temperature should I set my thermostat in winter?
About 68 °F while you're awake and 60 – 64 °F while sleeping or away.
Do setbacks work with heat pumps?
Yes, but keep them small or use smart recovery to avoid expensive backup heat.
Do I need a C-wire for a smart thermostat?
Most smart thermostats need one for constant power; some include a power adapter kit.
About SetbackSave
SetbackSave is an independent, free calculator estimating savings from thermostat setbacks, using the US Department of Energy rule of thumb of about 1 % per degree per 8 hours and published smart thermostat studies. Actual savings depend on your home, climate and habits. We are not affiliated with any thermostat brand or utility.
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