Thermostat Setback Savings Calculator
Estimate the savings from setting your thermostat back at night or while away, from your annual heating or cooling bill and the setback depth.
Calculator
Setting back 8 °F for 8 h/day saves roughly 8.0% ≈ $96.00/yr (heuristic ≈ 1% per °F over 8 h — an estimate, real savings vary).
Turning the thermostat down in winter (or up in summer) while you sleep or are away cuts the heat flowing in or out of the house, so the system runs less. The classic rule of thumb, from long-standing U.S. Department of Energy guidance, is that you save roughly 1% on the heating bill for each degree of setback over an 8-hour period. This tool applies that heuristic to your annual bill so the dollar figure is grounded in what you actually spend.
Enter your yearly heating (or cooling) cost, how many degrees you set back, and for how many hours a day. A deeper or longer setback saves more, up to a point — the same logic works for a single overnight setback or a combined night-plus-workday schedule. It is explicitly an estimate: real savings depend on your climate, insulation and how your equipment recovers.
Formula
The DOE-style heuristic, scaled to the setback length:
saving fraction = degrees × 1% × (setback hours ÷ 8)dollar saving = your annual cost × saving fraction
The (hours ÷ 8) term scales the rule of thumb, which is quoted for an 8-hour setback, to whatever schedule you keep. It is a linear approximation and does not model the recovery energy your system spends re-heating (or re-cooling) the house afterward, which is why it is labeled a heuristic rather than a measurement.
Worked example
A $1,200/yr heating bill, set back 8 °F for 8 hours a day:
- fraction = 8 × 1% × (8 ÷ 8) = 8%
- saving = $1,200 × 0.08 = $96/yr
Run two setback periods — 8 °F overnight and again 8 °F for 8 daytime hours while at work — and the modeled 16 hours of setback pushes the estimate toward 16%, about $192/yr. A shallower 4 °F setback over the same 8 hours saves about 4%, or $48/yr.
When the rule of thumb holds — and when it does not
The 1%-per-degree rule is a well-worn approximation, not a law. It holds best in milder climates and for well-controlled setbacks; in very cold weather, or with a heat pump using inefficient backup strips to recover, savings can be smaller — deep setbacks can even trigger costly electric-resistance recovery. A programmable or smart thermostat that recovers gradually captures the benefit without a comfort penalty.
To turn a percentage into a firmer dollar figure, start from a real annual bill; to see where that heating cost comes from in the first place, use the AC running cost, heat-pump running cost and furnace running cost tools. Efficiency upgrades such as a better SEER2 unit stack on top of setback savings.
Think of setback as free savings you schedule once and forget: unlike an equipment upgrade, it costs nothing to enable and pays back immediately. The biggest gains come from the hours nobody is comfortable anyway — deep in the night, or the empty house during a workday. Pair a modest, consistent setback with the tighter envelope and higher-efficiency equipment the other tools help you plan, and the percentages compound into a noticeably smaller bill without any hit to day-to-day comfort.
Reference table
Estimated saving on a sample $1,200/yr bill by setback depth and daily hours (enter your own bill in the tool):
| Setback | 8 h/day | 16 h/day |
|---|---|---|
| 4 °F | 4% · $48 | 8% · $96 |
| 6 °F | 6% · $72 | 12% · $144 |
| 8 °F | 8% · $96 | 16% · $192 |
| 10 °F | 10% · $120 | 20% · $240 |