Smart Thermostat Energy Savings Calculator
Estimate your annual energy and cost savings by switching to a smart thermostat. Based on DOE/EPA ENERGY STAR methodology using setback temperature differentials and occupancy schedules.
Heating System
Recommended: 7–10°F for 8 hrs/dayCooling System
Recommended: 4–7°F for 8 hrs/daySmart Thermostat Details
Formulas Used
Heating Savings Rate (per day, as fraction of bill):
heating_savings_rate = (setback_°F × setback_hours) / (24 × 100)
Based on the DOE rule of thumb: each 1°F setback for 8 hours ≈ 1% savings, generalized to any setback magnitude and duration.
Annual Heating Savings:
annual_heating_savings = monthly_heating_bill × heating_months × heating_savings_rate
Annual Cooling Savings (cooling is ~15% less responsive per degree due to latent heat loads):
cooling_savings_rate = (setback_°F × setback_hours) / (24 × 100) × 0.85 annual_cooling_savings = monthly_cooling_bill × cooling_months × cooling_savings_rate
Net Investment & Payback:
net_investment = thermostat_cost + installation_cost − rebate payback_years = net_investment / total_annual_savings savings_N_years = (total_annual_savings × N) − net_investment
Assumptions & References
- DOE rule of thumb: saving 1% on heating/cooling costs for every 1°F setback maintained for 8 hours per day (energy.gov).
- Cooling savings factor of 0.85× accounts for latent (humidity) loads that reduce the proportional benefit of temperature setbacks in cooling mode.
- Savings rates are capped at 30% per season to reflect physical limits of setback strategies.
- ENERGY STAR estimates smart thermostats save an average of $50/year; actual savings range from $20–$200+ depending on climate and usage (energystar.gov).
- Rebates from utilities or the federal Inflation Reduction Act (up to $50–$100 in many programs) reduce net investment.
- Results do not account for HVAC system efficiency (AFUE/SEER ratings), home envelope quality, or local climate severity.
- Installation cost is $0 for DIY-compatible systems; professional installation typically costs $75–$150.