Smart thermostat savings estimate
Updated
Enter your heating and cooling costs, the setback you would use and the thermostat price to see a realistic savings range and payback, based on ENERGY STAR and Department of Energy figures.
Next steps
How the calculation works
Nobody can promise a precise number, so the calculator shows a range built from two public figures. The Department of Energy says you can save as much as 10% a year on heating and cooling by turning the thermostat back 7–10°F for 8 hours a day. ENERGY STAR reports that homes with certified smart thermostats save on average 8% on heating and cooling costs, about $50 a year.
- Ceiling: annual heating and cooling cost × 10% × a setback factor × your habit factor.
- Typical: the same, with 8%.
- Cautious: the same, with 4%. This floor is our modeling choice (half of the ENERGY STAR average), not a published number. Real homes can save less.
The setback factor is your degrees × hours divided by 56 (the low end of DOE’s 7°F × 8 h example), capped at 1. A smaller setback scales the estimate down; a larger one does not raise it above the ceiling. The habit factor is 1.0 if you leave one setting all day, 0.6 if you adjust by hand now and then, 0.3 if you already run a schedule well, because the DOE savings come from the setback itself, not from owning a smart device.
Example 1 (the default): $1,000 a year, a 7°F drop for 8 hours, one setting today. Setback factor 1, habit factor 1. Range $40 to $100, typical $80. A $150 thermostat with no rebate pays back in 1.5 to 3.8 years.
Example 2: $120 a month over 6 months is $720 a year. A 5°F drop for 8 hours gives a setback factor of 40 ÷ 56 = 0.71, and you already adjust by hand (0.6). The range is about $12 to $31 a year, so a $150 thermostat takes roughly 4.9 to 12.2 years to pay back: not a good use of money on savings alone, unless a rebate cuts the price or you value the remote control.
Common mistakes
- Using the whole electric or gas bill. Only heating and cooling respond to a thermostat. ENERGY STAR notes that heating and cooling account for almost half of the average annual energy bill; your share may differ, especially with gas water heating or electric resistance heat.
- Expecting savings from the device alone. A smart thermostat that is left at one setting saves little. The savings come from lower temperatures at night and when no one is home. A programmable thermostat can do the same: see smart vs programmable thermostat.
- Ignoring the installation cost. Add a $20–$40 power adapter or a $100–$300 service call if you need a C-wire; the cost is in the C-wire guide. Subtract any utility rebate: see rebates and utility programs.
- Using big setbacks with a heat pump. The DOE generally does not recommend them for standard thermostats because of auxiliary heat. Use a thermostat designed for heat pumps.
Frequently asked questions
How much does a smart thermostat save on average?
ENERGY STAR reports that homes with certified smart thermostats save on average 8% on heating and cooling costs, about $50 a year. Your result depends on climate, system and habits.
Does the setback have to be 7–10°F?
The Department of Energy’s “as much as 10%” figure is based on turning the thermostat back 7–10°F for 8 hours a day. Smaller setbacks still save energy but less, which is why this estimate scales down.
Is a smart thermostat worth it if I already adjust my thermostat?
The savings are smaller, because you already capture much of the setback. The remaining benefits are convenience, remote control and occupancy-based changes, so the payback case rests less on energy.