Calculate energy savings from using a programmable thermostat with temperature setbacks. Estimate cost reduction from scheduled heating and cooling adjustments.
A programmable thermostat saves energy by automatically lowering the temperature when you're asleep or away from home. The Department of Energy estimates you can save about 1% on your heating bill for each degree of setback over an 8-hour period. A 7–10°F setback for 8 hours a day can save up to 10% annually.
The principle is simple: the rate of heat loss is proportional to the temperature difference between inside and outside. By reducing indoor temperature, you reduce this difference and slow heat loss. The energy saved during the setback period exceeds the extra energy needed to recover the temperature.
This calculator estimates savings from specific setback schedules, including separate daytime (away) and nighttime setback periods. It helps you find the optimal balance between comfort and savings.
Integrating this calculation into regular energy reviews ensures that conservation strategies are grounded in measured data rather than assumptions about building performance and usage patterns.
Many homeowners keep their thermostat at a constant temperature, wasting energy during unoccupied or sleeping hours. This calculator shows exactly how much money you can save by implementing different setback schedules. This quantitative approach replaces rough estimates with precise figures, enabling facility managers to identify the most cost-effective opportunities for reducing energy consumption.
Savings % ≈ 1% per degree of setback per 8 hours/day Adjusted Savings = Heating Cost × (Setback Degrees × Setback Hours / 8) × 1% Total Savings = Away Savings + Night Savings
Result: $195/year savings
Away setback: 8°F for 8 hrs = 8% savings on heating. Night setback: 5°F for 8 hrs = 5% savings. Combined: ~13% but with overlap adjustment ≈ $195/year on a $1,500 heating bill.
Heat loss is governed by Newton's law of cooling: the rate of heat loss is proportional to the temperature difference between inside and outside. If it's 30°F outside and 70°F inside (ΔT = 40°F), your furnace works to replace heat lost at that rate. Lowering to 62°F (ΔT = 32°F) reduces heat loss by 20% during that period.
The ideal setback schedule balances savings and comfort. Two 8-hour setback periods (away + sleeping) with 5–10°F reduction each provide the best results. Recovery should begin 30–60 minutes before you need full comfort. Excessive setbacks (>10°F) can cause long recovery times and temporary discomfort.
Well-insulated homes cool slowly, making setbacks even more effective — the temperature may only drop 3–4°F during a short absence even without heating. Poorly insulated homes cool faster, meaning the furnace is off for a shorter portion of the setback period, but savings still occur.
The DOE estimates 10% annual savings with proper use. Real-world savings vary from 5–15% depending on climate, setback degrees, hours per day, and building insulation. In cold climates with high heating bills, dollar savings are larger.
Setbacks save energy. The myth that "it takes more energy to reheat" is false in virtually all cases. The energy saved during the setback period always exceeds the recovery energy, because heat loss is proportional to the temperature difference.
Use smaller setbacks (2–4°F) with heat pumps. Large setbacks can trigger auxiliary electric resistance heat during recovery, which is very expensive. Smart thermostats manage this automatically; programmable thermostats may not.
For heating: 7–10°F setback during 8+ hours of absence is optimal. A 68°F daytime / 60°F overnight schedule saves 8–10% while maintaining comfort. For cooling: raise the setpoint 4–7°F when away.
Studies show 40–50% of programmable thermostat owners never program them, often due to confusing interfaces. This is why smart thermostats that learn schedules automatically are so popular — they capture savings without requiring user programming.
Yes. Raising the thermostat 7–10°F for 8 hours while you're at work saves 5–10% on cooling costs. The same principle applies: reducing the indoor-outdoor temperature difference reduces the rate of heat gain.