What is your air conditioner's SEER worth?
Convert SEER to SEER2, see what a new unit saves, or check the federal minimum for your region.
Factors are AHRI's, adopted by RESNET: SEER2 ÷ SEER is 0.95 for ducted systems and 1.00 for ductless.
A ton of cooling is 12,000 BTU/h. For minimums, capacity matters only for split-system air conditioners (under or over 45,000 BTU/h).
Use SEER for both units or SEER2 for both, never one of each.
Examples only: your climate, house and thermostat set the hours, and your bill sets the price (see the electricity cost calculator).
Southeast: AL, AR, DE, FL, GA, HI, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, DC and the territories. Southwest: AZ, CA, NV, NM. Regions change the rules only for air conditioners.
Check a unit, optional
What is the difference between SEER and SEER2?
Both rate the cooling a system delivers over a season, in BTU, per watt-hour of electricity it uses; higher is better. SEER2 comes from the revised federal test procedure (Appendix M1 of 10 CFR 430 Subpart B), and since January 1, 2023 the DOE standards are written in SEER2, HSPF2 and EER2. DOE notes these ratings are similar to the old ones but not directly comparable, so a unit is judged on its own SEER2, not on a converted number. A DOE final rule of January 7, 2025 also adopted new SCORE and SHORE metrics for a future test procedure, but they are not required until DOE issues amended standards based on them, so SEER2 is still the rating in force.
How do I convert SEER to SEER2?
Multiply SEER by 0.95 for ducted split systems and ducted packaged units, and by 1.00 for ductless systems; for heat pump heating, multiply HSPF by 0.85 (split), 0.84 (packaged) or 0.90 (ductless) to get HSPF2. Divide to go the other way. These factors were developed by AHRI and adopted by RESNET (MINHERS Addendum 71f, February 2023) — DOE itself publishes no single multiplier. A 16 SEER ducted split system is about 16 × 0.95 = 15.2 SEER2. DOE's own translation of its minimum levels shows the same size of drop: 14 SEER became 13.4 SEER2, 15 became 14.3, and 8.8 HSPF became 7.5 HSPF2.
What is the minimum SEER2 for a new air conditioner or heat pump?
Since January 1, 2023, DOE requires at least 13.4 SEER2 for split-system and single-package air conditioners, 14.3 SEER2 and 7.5 HSPF2 for split-system heat pumps, and 13.4 SEER2 and 6.7 HSPF2 for single-package heat pumps. Split-system air conditioners installed in the Southeast or Southwest must reach 14.3 SEER2 (13.8 from 45,000 BTU/h up), and in the Southwest an EER2 minimum applies too: 11.7 (11.2 from 45,000 BTU/h) below 15.2 SEER2, 9.8 at 15.2 or more, and 10.6 for single-package units. The Southeast is Alabama, Arkansas, Delaware, Florida, Georgia, Hawaii, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, D.C. and the territories; the Southwest is Arizona, California, Nevada and New Mexico; every other state is the North.
How do I estimate what an air conditioner costs to run, and what a new one saves?
SEER is BTU of cooling per watt-hour, so kWh a year = BTU/h × full-load hours ÷ SEER ÷ 1,000, and a ton is 12,000 BTU/h. A 3-ton unit (36,000 BTU/h) at 10 SEER for 1,000 full-load hours uses 36,000 × 1,000 ÷ 10 ÷ 1,000 = 3,600 kWh; at 16 SEER it uses 2,250 kWh. The 1,350 kWh difference is $202.50 a year at 15 cents per kWh. Full-load hours depend on your climate, house and thermostat, and the 1,000 and 15 cents here are only examples — use your own, and see the electricity cost calculator for your appliance's price per kWh.
How are SEER, EER and COP related?
EER is the cooling in BTU per hour divided by the watts drawn at 95 °F, a peak-load rating; SEER is the seasonal version. COP is the same ratio without units: COP = EER ÷ 3.412, because a watt-hour is 3.412 BTU. When the EER is not known, the NREL Building America protocols suggest the approximation EER = −0.02 × SEER² + 1.12 × SEER, after a 2003 University of Colorado thesis by Wassmer: 14 SEER gives about 11.8 EER, or a COP near 3.4. It is only an estimate, for the old SEER scale; the rated EER on the nameplate is the real number.
Sources: U.S. DOE, 10 CFR 430.32(c)(5) and (c)(6) and “Central Air Conditioners: 2023 Standards FAQ” (October 5, 2022); Federal Register 82 FR 1786 (January 6, 2017) and 90 FR 1224 (January 7, 2025); RESNET MINHERS Addendum 71f, SEER2 and HSPF2 Conversions (February 10, 2023); NREL, Building America House Simulation Protocols (2010); EIA, British thermal units. Room air conditioner size: BTU calculator. Price per kWh: electricity cost calculator. Heat pump versus fuel: heating cost calculator. How we check our calculators.