Energy Savings Calculator (Old vs New HVAC System)
Compare the energy costs of your old HVAC system versus a new high-efficiency unit to estimate your annual and lifetime savings.
Seasonal Energy Efficiency Ratio of existing unit (typically 6–14 for older systems)
SEER2 rating of new unit (modern systems: 14–26+)
Cooling capacity of the HVAC system (1 ton = 12,000 BTU/hr)
Estimated hours the AC runs per year (varies by climate; 800–2000 typical)
Your local utility rate per kilowatt-hour (U.S. average ~$0.13/kWh)
Expected lifespan of the new HVAC system (typically 15–20 years)
Total installed cost of the new HVAC system (optional, for payback calculation)
Formulas Used
Power Draw (kW):
kW = (Tons × 12,000 BTU/hr) ÷ (SEER × 1,000)
Annual Energy Consumption (kWh):
Annual kWh = kW × Annual Cooling Hours
Annual Energy Cost ($):
Annual Cost = Annual kWh × Electricity Rate ($/kWh)
Annual Savings:
Annual Savings = Old Annual Cost − New Annual Cost
Lifetime Savings:
Lifetime Savings = Annual Savings × System Lifetime (years)
Simple Payback Period:
Payback (years) = Installation Cost ÷ Annual Savings
CO₂ Reduction:
CO₂ Saved (kg) = kWh Saved × 0.386 kg CO₂/kWh
(EPA eGRID national average emission factor)
Assumptions & References
- SEER (Seasonal Energy Efficiency Ratio) measures cooling output (BTU) per watt-hour of electricity consumed over a typical cooling season.
- 1 ton of cooling = 12,000 BTU/hr of heat removal capacity.
- Power draw formula: kW = (Tons × 12,000) ÷ (SEER × 1,000) — derived from the SEER definition (BTU/Wh converted to kW).
- New systems are rated under SEER2 (DOE 2023 standard), which uses a slightly more rigorous test; SEER2 values are approximately 5% lower than equivalent SEER values. Enter the rated value from your equipment documentation.
- Annual cooling hours vary significantly by climate zone: ~500–800 hrs (northern U.S.), ~1,200–1,800 hrs (mid-Atlantic/Midwest), ~2,000–3,000 hrs (southern U.S./Sun Belt).
- U.S. average residential electricity rate: ~$0.13/kWh (EIA, 2024). Rates vary widely by state ($0.09–$0.35+/kWh).
- CO₂ emission factor: 0.386 kg CO₂ per kWh — EPA eGRID 2022 U.S. national average for electricity generation.
- Calculation covers cooling energy only. Heating efficiency (HSPF/AFUE) is not included.
- Savings assume consistent usage patterns and do not account for electricity rate inflation, maintenance costs, or rebates/tax credits (e.g., IRA Section 25C: up to $600 credit for qualifying HVAC equipment).
- References: DOE SEER2 Standard (10 CFR Part 430), EPA eGRID 2022, EIA Electric Power Monthly (2024), ENERGY STAR HVAC guidelines.