SEER to SEER2 converter

What is the SEER to SEER2 conversion factor?

The Department of Energy switched from SEER to SEER2 in January 2023 with the M1 testing procedure. To convert a legacy SEER rating to its SEER2 equivalent, multiply by one of three numbers depending on the equipment type:

• Split central air conditioner: SEER2 = SEER × 0.95
• Split heat pump: SEER2 = SEER × 0.93
• Single-package unit (rooftop, packaged AC): SEER2 = SEER × 0.92

Going the other way, divide. So a SEER2 16 split AC equals legacy SEER 16 ÷ 0.95 = 16.84. The reason it is a multiplication and not a flat adjustment is that SEER2 testing happens at five times the external static pressure (0.5 inches of water column vs 0.1), and that static pressure penalty is roughly proportional to the rated efficiency. A SEER 22 unit loses more SEER points in the conversion than a SEER 14 unit.

SEER to SEER2 conversion chart for common AC ratings

Quick lookup for split central air conditioners (multiplier 0.95). Multiply by 0.93 for split heat pumps, 0.92 for single-package units.

• SEER 10 = SEER2 9.50
• SEER 13 = SEER2 12.35
• SEER 14 = SEER2 13.30 (old federal minimum, no longer compliant)
• SEER 15 = SEER2 14.25 (close to new minimum)
• SEER 16 = SEER2 15.20
• SEER 18 = SEER2 17.10
• SEER 20 = SEER2 19.00
• SEER 22 = SEER2 20.90
• SEER 24 = SEER2 22.80

Federal minimum SEER2 ratings for new AC installs

The DOE final rule that took effect January 1, 2023 set new minimums by region. If you are buying a new central AC, it has to meet these to be legally installed.

• Northern states (north of the 36th parallel): SEER2 13.4 split central AC, SEER2 14.3 heat pump
• Southern states (south of the 36th parallel): SEER2 14.3 split central AC, SEER2 14.3 heat pump
• Southwest (CA, AZ, NV, NM, southern UT): SEER2 14.3 plus EER2 11.7 (the dry-climate requirement)
• Single-package units anywhere: SEER2 13.4, EER2 10.6
• Mini splits and multi-split heat pumps: SEER2 14.3, HSPF2 7.5

A SEER 14 unit, which was the federal minimum before 2023, converts to SEER2 13.3. That is why a unit that was legal to install in 2022 is no longer legal in southern states. Inventory of pre-2023 units could still be sold and installed through specific sell-through dates that varied by region, but new manufacturing must hit the SEER2 minimums.

Why SEER2 numbers look lower than your old AC unit rating

A common reaction when homeowners shop for a new AC: "My old unit was SEER 16. Why is this new one only SEER2 15?" The answer is the conversion. SEER2 15 on the new unit is roughly the same real-world efficiency as SEER 15.8 on the old test. The new test does not make your AC less efficient. It just measures more honestly. If anything, the new SEER2 rating tells you something closer to what you will actually experience with your home's ductwork.

How SEER2, EER2, and HSPF2 relate to your power bill

Three ratings to know when you shop:

• SEER2: seasonal cooling efficiency, the everyday number for sizing your bill.
• EER2: steady-state cooling efficiency at 95 degrees outside, matters in extreme heat.
• HSPF2: heating seasonal performance factor for heat pumps, the heating version of SEER2.

For most homeowners SEER2 drives the cooling cost. HSPF2 drives the heating cost on a heat pump. EER2 only matters in places like Phoenix and Las Vegas where the AC runs at peak load for hours every summer day. Brands market SEER2 hardest because the number is largest. Always ask for all three on the AHRI certificate before signing a quote.

Brand differences: do Carrier, Trane, and Lennox report SEER2 the same way?

Yes. All AC ratings have to be certified through AHRI (Air-Conditioning, Heating, and Refrigeration Institute), and the test method is identical across brands. A Carrier Infinity 24 SEER2 unit and a Trane XV20i SEER2 21 unit went through the exact same M1 test procedure with the exact same instruments. The differences in real-world performance come from compressor staging, blower motor quality, controls, and matched-pair coil sizing, not from any rating game. Goodman, Rheem, Lennox, Carrier, Trane, Daikin, Mitsubishi, and Bosch all report SEER2 on the same scale.

What SEER2 rating do you need to meet code?

Federal code is just the floor. Most local building departments and many utility rebate programs require higher minimums than the DOE baseline. Energy Star certification for central AC currently requires SEER2 15.2 split, SEER2 14.3 single-package, plus an EER2 floor. To qualify for most utility rebates of $400 to $1,500, you need Energy Star or higher. For utility heat pump rebates the bar is usually SEER2 15.2 and HSPF2 8.1 minimum, with bigger rebates at SEER2 17+ and HSPF2 9+.

California Title 24, the strictest state code in the country, requires SEER2 14.3 and EER2 11.7 in dry climate zones. New York and Massachusetts state codes require Energy Star for new construction. If you are not sure what your jurisdiction requires, call your local building department before signing an HVAC contractor quote.

How AHRI matched-pair ratings actually work

A SEER2 rating only applies to a matched indoor and outdoor unit pair, not the outdoor condenser alone. The same Carrier 24ACB7 condenser paired with three different evaporator coils will give you three different AHRI-certified SEER2 ratings. This is the trick contractors sometimes use: they quote the highest-SEER2 matched pair in marketing, then install the cheaper coil that drops the real rating by 1 to 2 SEER2 points. Before you sign a quote, demand the AHRI certificate number for the exact indoor and outdoor unit pair on the installation. Look it up at ahridirectory.org to confirm the SEER2 number on the bid matches the certified rating for that pair.

SEER, SEER2, and what comes next

The DOE updates testing procedures roughly every 10 to 15 years. SEER replaced the original EER rating in 1992. SEER2 replaced SEER in 2023. The next likely update will tighten cold climate heat pump testing and add a new "low temperature" rating for heat pumps in zones 5 through 7. There are no concrete plans for a SEER3 rating in the near term, but anything you buy today is rated under the current SEER2 / EER2 / HSPF2 trio and that will not change for the equipment lifetime.