Thermostat Setback Calculator

Estimate savings from thermostat setback.

Annual heating bill

Degrees of setback

°F

Hours per day at setback(optional)

hrs

e.g. while asleep or away

Results update as you type.

Estimated savings

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Annual savings—

How it works

Turning your thermostat down when you're asleep or away saves energy, and this calculator estimates how much. You enter your annual heating bill, how many degrees you set the thermostat back, and how many hours per day the setback lasts, and it returns the estimated percentage savings and annual dollar savings. The estimate is based on a well-known U.S. Department of Energy rule of thumb: you can save around 1 percent on your heating bill for each degree of setback sustained over an eight-hour period. So setting back 8 degrees for 8 hours a day (for example, overnight) saves roughly 8 percent. The calculator scales the savings by both the number of degrees and the length of the setback relative to eight hours. The savings come from the fact that a building loses heat more slowly when the indoor temperature is closer to the outdoor temperature, so a cooler house during setback hours loses less heat and needs less energy to maintain. A programmable or smart thermostat makes this effortless by automatically lowering the temperature at set times and warming the home before you wake or return. The rule works best in winter heating; cooling setback (turning the AC up when away) saves similarly in summer. Enter your bill, setback degrees, and hours to estimate the savings.

Formula

Savings % ≈ degrees setback × (hours/day ÷ 8) × 1%

A common rule of thumb is that you save about 1 percent on heating for each degree of setback maintained over an 8-hour period. The calculator scales this by the degrees and the fraction of an 8-hour period the setback lasts, then applies it to your annual bill.

Source:U.S. Department of Energy thermostat guidance

We review all our tools from time to time to ensure accuracy.

Worked example

Annual heating bill:1200Degrees of setback:8Hours per day at setback:8

8 degrees over 8 hours ≈ 8% savings; on a $1,200 bill, about $96 a year.

How to use this calculator

1
Enter your values
Enter annual heating bill and degrees of setback.
2
Adjust the options
Adjust hours per day at setback if they apply — sensible defaults are already set.
3
Read your result
Estimated savings updates instantly as you type — no button to press.

Frequently asked questions

How much does turning down the thermostat save?

A U.S. Department of Energy rule of thumb is about 1 percent off your heating bill per degree of setback over an eight-hour period. Setting back 8 degrees for 8 hours saves roughly 8 percent — about $96 on a $1,200 annual bill. Larger or longer setbacks save more, which this calculator estimates.

Why does setting back the thermostat save energy?

A building loses heat faster the greater the difference between indoor and outdoor temperatures. Lowering the thermostat during setback hours shrinks that difference, so the home loses heat more slowly and the heating system runs less to maintain the cooler temperature. Over hours each day, this reduced heat loss translates into meaningful energy and cost savings.

Does the house use extra energy to reheat?

The energy to reheat is less than what's saved during setback, so setting back still nets savings — a common myth claims otherwise. Because the house loses less heat while cooler, the total energy used is lower even including the reheat. This holds for typical setback periods; the savings are real, which is why the rule of thumb applies.

When should I set back the thermostat?

Common setback times are overnight while sleeping and during the day when the house is empty — periods of several hours when a cooler home is comfortable or unnoticed. A programmable or smart thermostat automates this, lowering the temperature on schedule and warming the home before you wake or return, capturing the savings without any daily effort.

Does this apply to air conditioning too?

Yes, in reverse. In summer, setting the thermostat higher (letting the home get warmer) while away or asleep reduces cooling energy the same way, since a warmer indoor temperature is closer to the hot outdoors and the AC runs less. The same rule-of-thumb logic applies to cooling setback, saving on air conditioning costs.