SEER2, HSPF2 and EER2: Why a Mini Split Rating Cannot Be Compared With an Older Number

Amazon turns the bare prefix seer2 into seer2 mini split, seer2 24 mini split, seer2 25 and seer2 22. We pulled those completions on October 1, 2026. Shoppers are typing the metric itself, which means they are comparing two boxes that may not be comparable.

We have tested nothing, and no number here is a measurement of ours. Everything below is read off the Code of Federal Regulations, three Federal Register rules opened through GovInfo, the ENERGY STAR criteria page and manufacturer specification sheets. We name a product only where the maker publishes the full rating set on a page anyone can open, which is also how we picked the examples.

Trend Signal

64/100 Steady momentum

1. Emerging
2. Rising
3. Mainstream
4. Peaking
5. Cooling

The metric changed once in 2023 and the next one is already written into the CFR

DOE said in 82 FR 1426, the rule that created the metrics, that SEER2, EER2 and HSPF2 are based on the previous metrics but generally have different numerical values. The appendix defining them now points to appendix M2 and the SCORE and SHORE metrics as the next step.

Our editorial reading of the cited data, not a forecast. How it is scored

By the numbers

• 14.3 SEER2Federal cooling minimum for split-system heat pumps made on or after Jan. 1, 2023eCFR 10 CFR 430.32
• 7.5 HSPF2Federal heating minimum for the same class, stated for DOE climate Region IVeCFR 10 CFR 430.32
• 8.8 HSPFThe level DOE translated into 7.5 HSPF2 when it converted the 2023 standardFederal Register 82 FR 1786
• 15.2 SEER2ENERGY STAR cooling threshold for heat pump split systems, read Oct. 1, 2026ENERGY STAR

Where SEER2, HSPF2 and EER2 came from

On January 5, 2017, DOE published a final rule amending the test procedure for central air conditioners and heat pumps at 82 FR 1426. Its summary says the new appendix M1 establishes new efficiency metrics SEER2, EER2 and HSPF2 that are based on the current metrics for cooling and heating performance, but generally have different numerical values than the current metrics. That sentence is the whole problem in one line, from the agency that created it.

The same rule lists the changes behind the new numbers: higher external static pressure requirements for all units, with separate minimums for mobile home, ceiling-mount and wall-mount systems; a new default fan power for coil-only units; a revised heating load line equation in the HSPF2 calculation; and amended testing for variable-speed heat pumps, including a 5°F heating mode test option for full-speed performance below 17°F.

Two of those matter differently by product. The static pressure change is a ducted problem: the appendix M1 text in that rule sets non-ducted air volume rates at an external static pressure of zero inches of water. A wall-mounted mini split blows into the room, so the pressure change does not reach it. The revised heating load line does, which is why the heating number moved for everyone.

DOE did not rescale the old numbers. It changed the measurement, and the numbers landed elsewhere.

The conversion DOE published, and what it proves

The standards rule that set the current floors is 82 FR 1786, published January 6, 2017. Its Table I-1 states the amended standards in the metrics of the day: for split-system heat pumps, 15 SEER and 8.8 HSPF, applying from January 1, 2023. DOE then translated those levels into the new procedure, and 10 CFR 430.32(c)(5) now requires 14.3 SEER2 and 7.5 HSPF2.

That is the cleanest proof a shopper will get that the numbers are not interchangeable. One level of efficiency, two metrics, two different figures: 15 becomes 14.3, and 8.8 becomes 7.5. DOE said it translated HSPF levels to HSPF2 by adjusting for the intermediate heating load line slope factor, using interpolation.

Set that against the previous floor at 10 CFR 430.32(c)(1): 14 SEER and 8.2 HSPF for the same class from January 1, 2015. A leftover 2022 unit can advertise 8.2 HSPF while a stricter 2026 unit advertises 7.5 HSPF2, and the second is the better machine. The same trap appeared in air purifiers, where the measurement changed under a familiar label, in air purifier efficiency standards.

Split-system heat pumps	Cooling	Heating
Federal minimum, made Jan. 1, 2015 to Dec. 31, 2022	14 SEER	8.2 HSPF
The 2023 level as DOE first wrote it, old test procedure	15 SEER	8.8 HSPF
The same level translated into the current regulation	14.3 SEER2	7.5 HSPF2
ENERGY STAR threshold, read October 1, 2026	15.2 SEER2	7.8 HSPF2

HSPF2 is a Region IV number, not yours

Appendix M1 is explicit about the climate behind the heating rating. For certifying compliance, section 5.1 says to use the fractional heating bin hours specified for Region IV to determine HSPF2, and section 5.2 makes representations for any other region optional. The certified heating number describes one DOE climate region; anything else is what a manufacturer chooses to publish.

Some do, and the gap is visible. Pioneer lists Heating HSPF2 for Region IV and Region V side by side on its product pages: 10.0 and 8.6 on a 12,000 Btu/h 115-volt wall unit, 9.5 and 8.2 on the 23,000 Btu/h model in the same series. A buyer in a colder region reading only the headline figure is reading the warmer of the two numbers the maker measured.

EER2 has a parallel quirk. Section 5.2 makes representations of EER2 optional for models not subject to regional EER2 standards, which is why a mini split spec sheet may show SEER2 and HSPF2 and omit EER2. Where it appears, it describes steady performance at a 95°F outdoor condition rather than a season.

Read the heating number as Region IV unless the page says otherwise, and look for a second column.

What ENERGY STAR and AHRI add on top

The federal minimum is a floor, not a grade. ENERGY STAR’s heat pump pages, read October 1, 2026 and dated by the program effective January 1, 2023, require at least 7.8 HSPF2, 15.2 SEER2 and 11.0 EER2 for split systems. The cold climate tier is stricter: 8.5 HSPF2 for non-ducted split systems and 8.1 for ducted ones, both at 15.2 SEER2.

The cold climate designation also requires low-ambient evidence rather than a seasonal average. A unit must show a coefficient of performance at 5°F of at least 1.75, measured by the appendix M1 H4 test, and heating capacity at 5°F of at least 70 percent of its capacity at 47°F. It must also pass a controls verification procedure confirming the unit’s native controls reach those figures as they would in a home. That is the part a seasonal number cannot tell you, and it is the number that matters in January.

AHRI sits underneath all of it. Its product performance certification program is voluntary and exists to confirm that products perform according to manufacturers’ published claims. The public side of the AHRI Directory lets anyone search certified ratings by product line or brand, and a manufacturer page printing an AHRI reference number is handing you the lookup key.

The next metric is already written into the rule

Appendix M1 as it stands today is not the appendix M1 of 2023. DOE amended it in a final rule published January 7, 2025 at 90 FR 1224, incorporating AHRI 210/240-2024 as the industry test standard behind SEER2 and HSPF2, with testing to the amended procedure mandatory from July 7, 2025. The CFR text carries a note to that effect.

The same rule wrote the next change into the regulation. It incorporated AHRI 1600-2024 for a new appendix M2 adopting two metrics, seasonal cooling and off-mode rating efficiency and seasonal heating and off-mode rating efficiency, known as SCORE and SHORE. DOE said testing to those is not required until compliance is required with amended standards based on them, and the appendix M1 note says representations must move to appendix M2 at that point.

For a shopper in October 2026 nothing changes: SEER2 and HSPF2 are the numbers on the box, and the refrigerant question in the R-410A phase-out explainer matters more to a purchase than a future metric. What it means is that the comparison problem is structural, which is what heat pump prices in 2026 and the 120-volt heat pump water heater guide both turn on. The filter aisle has the same lesson in miniature in the MERV rating explainer.

Compare two SEER2 figures or two SEER figures, never one of each.

What to watch next

• Any DOE standards rulemaking that sets levels in SCORE and SHORE, the trigger that moves representations to appendix M2
• The ENERGY STAR heat pump criteria page for a revision above 15.2 SEER2 and 7.8 HSPF2
• Whether more makers publish HSPF2 for a second DOE region next to the certified Region IV figure

Where to start

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More: Energy and Sustainability trends and how the Trend Signal is scored.

Questions readers ask

What is the difference between SEER and SEER2?

SEER2 is measured under DOE appendix M1, established in a 2017 test procedure rule. DOE wrote there that SEER2, EER2 and HSPF2 are based on the previous metrics but generally have different numerical values. Appendix M1 raised external static pressure requirements, changed default fan power for coil-only units and revised the heating load line equation.

What SEER2 and HSPF2 does a mini split have to meet?

10 CFR 430.32(c)(5) requires split-system heat pumps made on or after January 1, 2023 to reach at least 14.3 SEER2 and 7.5 HSPF2. Space-constrained heat pumps sit lower in the same table, at 11.9 SEER2 and 6.3 HSPF2.

Is HSPF2 the same everywhere in the country?

No. Appendix M1 says HSPF2 for certifying compliance uses the heating bin hours for Region IV, and that representations for other regions are optional. One maker we read lists 10.0 for Region IV and 8.6 for Region V on the same model.

Are SEER2 and HSPF2 about to be replaced?

DOE incorporated a new appendix M2 with the SCORE and SHORE metrics in a final rule published January 7, 2025. Testing to those metrics is not required until compliance is required with amended standards based on them, and representations stay on appendix M1 until then.