Smart Thermostat Schedule Savings Calculator
Estimate the heating and cooling savings from a smart thermostat schedule, based on how many degree-hours of setback it applies each day.
How it works
Setback degree-hours/day = setback °F × hours · Saving % = degree-hours ÷ 8 × (% per °F), capped · Saving = bill × saving%
The classic Energy Star rule is that each 1°F of setback held for about eight hours saves roughly 1% on heating and cooling. This calculator generalizes it to degree-hours: a bigger temperature setback or more hours per day both add up, so an 8°F setback for 14 hours does far more than a 4°F one for 8. A smart thermostat’s edge is applying that schedule reliably — and learning your patterns — where a manual thermostat gets forgotten. The saving is capped because setbacks show diminishing returns as the house spends more time at the reduced setpoint.
Worked example
An 8°F setback for 14 hours a day is 112 degree-hours. Divided by the 8-hour basis that is 14 units, and at ~1% each the model estimates a 14% cut. On a $1,200 annual heating and cooling bill that is about $168 saved a year.
Frequently asked questions
Is the 1%-per-degree rule reliable?
It is a well-known Energy Star rule of thumb that works best for setbacks of about 8 hours in mild-to-moderate climates. In very cold climates or with heat pumps the savings can be smaller, so treat the output as an estimate and tune the per-degree figure to your situation.
Do setbacks cost more when the system catches up?
The recovery energy to reheat or recool a house is real but smaller than the energy saved while the setpoint was lowered, so net savings remain positive. Smart thermostats reduce recovery cost further by pre-conditioning gradually rather than blasting the system.
Does this apply to heat pumps?
Deep setbacks can be less effective with heat pumps because recovery may trigger inefficient backup heat. Many smart thermostats have a heat-pump-aware mode that uses smaller setbacks — lower the setback value here to reflect that.
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This calculator is for educational purposes. Double-check important results before acting on them.