Thermostat Savings Calculator
Estimate heating savings from turning the thermostat down, using the ~1% per degree per 8 hours rule of thumb.
How it works
savings % ≈ degrees of setback × (hours ÷ 8) × 1% · monthly savings = heating cost × savings %
A long-standing rule of thumb holds that turning your thermostat back about 1% of heating cost per degree, per eight hours a day. The calculator applies that to the degrees you set back (current minus setback temperature) and the hours you hold it, then multiplies by your heating bill. This is a rough approximation, not a guarantee — real savings depend on insulation, climate, your heating system and how the house holds temperature.
Worked example
Lowering the thermostat from 70°F to 62°F — 8 degrees — for 8 hours a day is about 8 × (8 ÷ 8) × 1% = 8% off heating. On a $150 monthly heating bill that’s roughly $12 a month, or about $144 over a heating year.
Frequently asked questions
How reliable is the 1%-per-degree rule?
It’s a ballpark, most dependable for modest setbacks of around 5–10°F held over the standard 8-hour period the rule assumes. Larger or longer setbacks don’t scale up perfectly linearly, so treat big numbers here as optimistic and verify against your actual bills.
Doesn’t reheating a cold house cancel the savings?
It’s a common myth. It costs less to reheat a cooled house than to hold it warm the whole time, because a cooler house loses heat more slowly — the setback period saves more than the brief reheat spends.
Does the same idea work for air conditioning?
Yes, in reverse — setting the thermostat higher while you’re out saves on cooling by a similar rule of thumb. Heat pumps are the exception: aggressive setbacks can trigger inefficient backup heat, so use smaller ones and let a smart thermostat manage the recovery.
Related calculators
This is a rough rule-of-thumb estimate, not a guaranteed figure. Actual savings vary with your home, climate and heating system.