SEER Energy Savings Calculator
Compare the yearly cooling cost of an old and a new air conditioner or heat pump by SEER or SEER2 rating, with heating savings by HSPF, payback on the new unit, lifetime savings, CO₂ avoided and savings at other ratings and climates.
How it works
SEER = seasonal cooling output (BTU) ÷ electricity used (Wh) · cooling kWh = capacity (BTU/hr) × full-load hours ÷ (SEER × 1,000) · heating kWh = capacity × heating hours ÷ (HSPF × 1,000) · yearly cost = kWh × price · savings = old cost − new cost · SEER ≈ SEER2 ÷ 0.955, HSPF ≈ HSPF2 ÷ 0.85 · payback = unit price ÷ yearly savings
SEER is the cooling a unit delivers over a season in BTU divided by the watt-hours it uses, so capacity × full-load hours ÷ (SEER × 1,000) gives the kilowatt-hours for the season. Doing that for both units and multiplying by your price per kWh gives two yearly bills, and the gap is the saving. Since 2023 US units are rated in SEER2, a tougher test that reads about 4.5% lower, so the calculator converts SEER2 back to SEER before comparing. For heat pumps the heating season works the same way with HSPF (or HSPF2, about 15% lower). An old unit rarely performs at its label, so you can take a few percent off it under More options. Savings follow 1/SEER, which means each extra point saves less than the one before: SEER 10 to 14 saves far more than 18 to 22. Enter the unit price to see the simple payback, and use the climate table to see how much the result depends on how hard your unit works.
Worked example
A 36,000 BTU/hr (3-ton) unit running 1,000 equivalent full-load hours uses 36,000 × 1,000 ÷ 10,000 = 3,600 kWh a year at SEER 10 and 36,000 × 1,000 ÷ 18,000 = 2,000 kWh at SEER 18. At $0.16/kWh that is $576 against $320, a saving of $256 a year (44%), or $3,840 over 15 years. If the new unit costs $7,500 installed, the energy savings alone take about 29 years to pay it back; at 2,500 cooling hours the saving is $640 a year and the payback about 12 years.
Sources: U.S. Department of Energy — central air conditioning and SEER2 minimum standards · U.S. EPA — eGRID power-sector CO₂ emission rates
Frequently asked questions
What are “equivalent full-load hours”?
It is the number of hours the unit would run at full capacity to deliver a season’s cooling. Real units cycle on and off, but collapsing that into full-load hours makes energy use easy to compute; 600–900 hours is typical for mild climates and 2,000–3,000 for hot, humid ones. The climate table under the results shows how the savings change with the hours.
Is a higher SEER always worth the extra cost?
Not always. Savings shrink with each SEER point because they scale with 1/SEER, so in a mild climate or with cheap power the payback on a very high-SEER unit can be long. Enter only the price difference between two models as the unit price to see how long the upgrade itself takes to pay back.
How does SEER2 compare to SEER?
SEER2 is the test standard used in the US since 2023. It uses higher external static pressure, so the same unit reads about 4–5% lower: SEER 14 is about SEER2 13.4 and SEER 15 about SEER2 14.3. Choose SEER2 next to the rating and the calculator converts it so both units are compared on the same scale.
Can I include heating savings for a heat pump?
Yes. Switch on the heat pump option and enter the heating hours and the HSPF (or HSPF2) of both units. Heating kWh is worked out the same way as cooling, and the results split the savings between the two seasons.
Why might my real savings differ?
Labels assume a correct install. Oversized units, leaky ducts, low refrigerant and dirty coils all cut efficiency, and your thermostat habits change the hours. Compare a year of bills before and after for the true figure.
Related calculators
Estimate only — actual savings depend on your climate, usage, installation quality and utility rates.