Thermostat Savings Calculator
Estimate annual HVAC savings from thermostat setback adjustments.
Each degree saves 1-3% on energy bills — calculate payback time for a smart thermostat.
Setting your thermostat at the optimal temperature balances comfort with energy savings. Heating and cooling typically account for 45–55% of a home’s energy bill in temperate climates — even small thermostat adjustments compound into significant annual savings.
Energy Savings formula (approximate):
Savings per Degree per Day ≈ 1% of heating/cooling cost per degree per 8 hours
More precise formula:
Heating Energy = (Indoor Temp − Outdoor Temp) × Hours × Building Heat Loss Rate / System Efficiency
What each variable means:
- Setpoint: the target temperature you program the thermostat to maintain
- Setback: the reduced temperature when away or sleeping (a lower heating setback saves money; a higher cooling setback saves money in summer)
- Building Heat Loss Rate: measured in BTU/hour per °F of temperature difference; depends on insulation, windows, and square footage; a typical 2,000 ft² home loses 15,000–25,000 BTU/h per 20°F difference
- System Efficiency (AFUE/SEER): a 95 AFUE furnace converts 95% of fuel to heat; a SEER 18 AC unit produces 18 BTU of cooling per watt-hour consumed
- Degree Days: a climate data metric; 1 heating degree day = 1 day where the average outdoor temperature is 1°F below 65°F
Worked example: House with $180/month heating bill. Owner installs a programmable thermostat and sets a 7°F setback for 8 hours per night + 8 hours away.
Savings ≈ 7° × (8 hr/24 hr) × 1%/degree = 7 × 0.333 × 1% = 2.33% per degree × hours per day With 7°F setback: savings ≈ 7°F × 1% per degree (US DOE rule of thumb) = ~7% on the heating portion Heating portion of $180: ~$100/month → Savings ≈ $7/month → $84/year
US DOE recommended thermostat settings:
- Winter: 68°F (20°C) when home; 60°F (15.5°C) when asleep or away
- Summer: 78°F (25.5°C) when home; 85°F (29.5°C) when away
- Each degree higher in winter or lower in summer costs roughly 3% more per degree per month
Smart thermostats (e.g., Nest, Ecobee) typically save $140–$180/year by learning your schedule and optimizing run times.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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