SEER2, EER2 and HSPF2: ratings and minimums explained

SEER2, EER2 and HSPF2 are the efficiency ratings used since January 1, 2023, under DOE’s M1 test, which runs at higher airflow resistance. Minimums: split ACs need 13.4 SEER2 in the North and 14.3 in the Southeast and Southwest (13.8 at 45,000 Btu/h and up). Split heat pumps need 14.3 SEER2 and 7.5 HSPF2 nationwide.

What changed in 2023

On January 1, 2023, DOE moved central air conditioners and heat pumps to a new test procedure, known as Appendix M1, with new rating names: SEER2, EER2 and HSPF2. The new test raises the external static pressure, the airflow resistance the blower works against, by up to five times, to better reflect ducts in real homes. The same equipment scores lower under M1, so SEER2 numbers look smaller than old SEER numbers.

DOE says the new and old ratings are similar but not directly comparable. When it set the 2023 standards, it translated each level from the old metric to the new one:

Use these to read old brochures, not to convert a specific model. For a real model, use the SEER2, EER2 and HSPF2 on its AHRI certificate.

What each rating measures

• SEER2: cooling delivered over a typical season divided by the electricity used. Higher is better.
• EER2: cooling efficiency at one hot condition, 95°F outdoors, when the system works hardest.
• HSPF2: heating delivered over a season divided by the electricity used, for heat pumps.
• AFUE: the share of fuel energy a furnace or boiler turns into heat. It has its own separate standard.

Federal minimums by region

Heat pump minimums are national. Air conditioners also have regional minimums in the Southeast and Southwest. In the North, the rule follows the date a unit was made, so an air conditioner built before 2023 to the old standard may still be installed there. In the Southeast and Southwest, a split air conditioner must meet the regional standard on the date it is installed.

Which states are in which region

• Southeast: Alabama, Arkansas, Delaware, Florida, Georgia, Hawaii, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, the District of Columbia, Puerto Rico and the other U.S. territories.
• Southwest: Arizona, California, Nevada and New Mexico.
• North: every other state.

DOE states plainly that it is illegal for a contractor to install a split air conditioner in the Southeast or Southwest that doesn’t meet the regional standard. It takes reports at [email protected].

How to check a unit’s rating

Ratings belong to the combination, not to the outdoor unit alone. DOE’s own guidance gives the example of one outdoor unit certified at 13.4 SEER2 with one indoor coil and at 14.3 SEER2 with another. Look up the exact outdoor unit, indoor coil and furnace or air handler from your quote in the AHRI Directory; the certificate lists SEER2, EER2 and HSPF2 for that match. If the combination isn’t listed, ask the contractor why before you sign.

Does a higher SEER2 pay off?

Estimate yearly cooling electricity as capacity in Btu/h × full-load cooling hours ÷ (SEER2 × 1,000). Full-load hours depend on your climate and thermostat habits. The example below assumes a 3-ton (36,000 Btu/h) system running 1,500 full-load hours a year at 16¢ per kWh.

Going from 14.3 to 18 SEER2 saves about $124 a year in this example. Simple payback is the extra cost divided by that saving, so each $1,000 of extra cost takes about 8 years to earn back. Double the cooling hours or the electricity price and the payback time halves. For scale, DOE estimated that the 2023 regional standard in the hot-dry Southwest would save a typical household about $150 over the life of the air conditioner.

A higher rating is most likely to pay off with a long cooling season, high electricity prices, or a rebate that requires it; ENERGY STAR central air conditioners need at least 15.2 SEER2. Installation quality matters as much as the label: ENERGY STAR says poor installation can cut efficiency by up to 30%.

Questions

Is 14.3 SEER2 the same as 15 SEER? At the level of the federal standard, yes: DOE translated the 15 SEER standard to 14.3 SEER2. For a specific model, use the SEER2 on its AHRI certificate rather than converting.

Can a contractor install a 13.4 SEER2 air conditioner in Texas? Not a split system under 45,000 Btu/h. Texas is in the Southeast region, where the minimum is 14.3 SEER2 (13.8 at 45,000 Btu/h and up). Packaged air conditioners have a 13.4 SEER2 minimum everywhere.

What SEER2 does ENERGY STAR require? ENERGY STAR central air conditioners must be rated at least 15.2 SEER2. Many utility rebates use ENERGY STAR or a higher tier as the bar.

Why do only Southwest states have an EER2 minimum? EER2 measures efficiency at 95°F, when the system works hardest. DOE set it for the hot-dry Southwest, where many cooling hours are spent at high outdoor temperatures.

Sources

• DOE: 2023 central air conditioner standards guidance — https://www1.eere.energy.gov/buildings/appliance_standards/pdfs/2023_CAC_Standards_FAQ_10-5-2022_Final.pdf
• DOE direct final rule, 82 FR 1786 (SEER to SEER2 translation) — https://www.govinfo.gov/content/pkg/FR-2017-01-06/html/2016-29992.htm
• DOE: Guidance on regional standards and matched combinations — https://www.energy.gov/sites/default/files/2022-06/cac_regional_guidance6-08-2022.pdf
• AHRI Directory of Certified Product Performance — https://www.ahridirectory.org/
• AHRI: 2023 energy efficiency standards — https://www.ahrinet.org/2023-energy-efficiency-standards
• DOE FEMP: Purchasing energy-efficient residential central air conditioners — https://www.energy.gov/cmei/femp/purchasing-energy-efficient-residential-central-air-conditioners
• ENERGY STAR: Heat and cool efficiently — https://www.energystar.gov/saveathome/heating-cooling