How to test a thermostat setback
Size a schedule and estimate the bill impact.
Pick the setback
Start with 7–8 °F for the hours you are asleep or away.
Set the schedule
Use a programmable or smart thermostat so the house is comfortable before you return.
Compare bills
Track two similar months and adjust the setback or hours from the observed difference.
What does this tool do?
A modest setback while you sleep or are away reduces run time without changing comfort much. The common rule of thumb is about 1% of the heating or cooling bill per degree Fahrenheit for an eight-hour setback; this tool applies that rule and shows the seasonal total.
The Formula
Savings % ≈ 1% × °F setback × (hours ÷ 8); saving = monthly bill × savings %Frequently Asked Questions
Does a setback damage the heating system?
For most furnaces and heat pumps a few degrees of setback is fine, though very large swings on older heat pumps can be inefficient. Follow the manufacturer guidance for your equipment.
Is it better to leave the thermostat constant?
Usually not. A setback for several hours saves more than the small extra energy needed to recover, especially in mild weather and well-insulated homes.