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.