Building Cooling Cost & Emissions Calculator
Calculate annual air conditioning electricity costs based on building size, SEER rating, and local climate. Use it when budgeting HVAC upgrades or comparing the operating cost of different cooling systems.
Last updated: September 2026
Formula below · 2 sources (climate.gov, Wikipedia) · Updated Sep 2026
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About this calculator
This calculator estimates annual cooling electricity cost with a simplified degree-hour method. The formula is: Cost = ((buildingSize × coolingDays × 24 × 0.8 × (85 − thermostatSetting)) / SEER / 1,000) × electricityRate. Building size × 0.8 BTU/h per sq ft per °F is an approximate whole-building heat-gain coefficient (envelope, infiltration and solar/internal gains lumped together), and coolingDays × 24 gives the cooling hours. The load is driven by the gap between an effective outdoor temperature of 85 °F during cooling hours and your thermostat setting, so a higher setting lowers the cost and settings of 85 °F or more give zero. Load (BTU) ÷ SEER (BTU per watt-hour) gives watt-hours; dividing by 1,000 converts to kWh, and multiplying by the electricity rate gives dollars. The result is a planning estimate for a house or small building; real costs depend on insulation, windows, sun exposure and local climate data (cooling degree days from NOAA).
How to use
Consider a 2,000 sq ft home with 120 cooling days per year, a SEER-13 system, electricity at $0.12/kWh, and a thermostat set to 75°F. Load = 2,000 × 120 × 24 × 0.8 × (85 − 75) = 46,080,000 BTU. Energy = 46,080,000 ÷ 13 ÷ 1,000 ≈ 3,545 kWh. Cost = 3,545 × $0.12 ≈ $425 per year. Upgrading to SEER-20 would cut energy by 35% (13/20), to about 2,304 kWh or $276 — saving roughly $149 per year. Raising the thermostat to 78°F would cut the original cost to about $298.
Frequently asked questions
What is a SEER rating and how does it affect my cooling electricity bill?
SEER stands for Seasonal Energy Efficiency Ratio and measures how many BTUs of cooling a system delivers per watt-hour of electricity consumed over an entire season. A higher SEER rating means the system uses less electricity to produce the same amount of cooling. For example, a SEER-20 unit uses 30% less electricity than a SEER-14 unit for identical cooling output. As of 2023, federal minimum standards in the US require at least SEER-14 in northern states and SEER-15 in southern states. Upgrading from a SEER-10 to a SEER-20 system can cut cooling costs nearly in half.
How do cooling degree days affect my annual air conditioning costs?
Cooling degree days (CDDs) measure how much and how long outdoor temperatures exceed a base temperature of 65°F over the course of a year. Cities like Phoenix accumulate over 4,000 CDDs per year while Minneapolis may see only 700, meaning cooling costs can be 5–6× higher in hot climates for identical buildings. This calculator uses cooling days × 24 hours with an effective 85 °F outdoor temperature as a proxy for annual cooling degree-hours, which simplifies the degree-day concept while still capturing regional climate differences. Accurate local CDD data is available from NOAA and utility companies and will give you the most reliable cost estimates.
How can I reduce building cooling costs without replacing my HVAC system?
Several no-cost and low-cost measures can meaningfully reduce cooling loads before you consider equipment replacement. Raising the thermostat by just 2°F can cut cooling energy use by 5–10%. Adding attic insulation and sealing air leaks can reduce heat infiltration by 15–25%, directly lowering the load your HVAC must handle. Exterior window shading — awnings, solar screens, or low-e window film — can cut solar heat gain by 40–60%. Smart thermostats that pre-cool during off-peak electricity rate hours can also reduce bills without reducing comfort.