Programmable Thermostat Savings Calculator

About the Programmable Thermostat Savings Calculator

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.

When This Page Helps

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.

How to Use the Inputs

1. Enter your annual heating cost.
2. Enter your normal thermostat setpoint.
3. Enter the setback temperature during away hours.
4. Enter the setback temperature during sleeping hours.
5. Enter the hours per day for each setback period.
6. Review estimated annual savings.

Example Calculation

Tips & Best Practices

• The 1% per degree per 8-hour rule is a reliable approximation.
• Don't set back more than 10°F — recovery time becomes excessive.
• Heat pumps should use smaller setbacks (2–4°F) to avoid expensive auxiliary heat during recovery.
• Setbacks work better in well-insulated homes that hold temperature longer.
• Set recovery to start 30–60 minutes before you need the full temperature.
• Night setbacks also improve sleep quality — 68°F is ideal for sleeping.

The Physics of Thermostat Setbacks

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.

Optimal Setback Strategy

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.

Setbacks in Different Building Types

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.

Frequently Asked Questions

• How much does a programmable thermostat save?

  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.

• Is it better to keep temperature constant or use setbacks?

  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.

• Should I use setbacks with a heat pump?

  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.

• What is the best setback temperature?

  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.

• Why don't most people use their programmable thermostat?

  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.

• Does setback save on cooling too?

  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.