Quick answer
SEER2 is the seasonal energy efficiency ratio of a central air conditioner or heat pump: the cooling it delivers over a typical season, in BTUs, divided by the electricity it uses, in watt-hours, measured under the federal Appendix M1 test that took effect on 1 January 2023.
A higher SEER2 means less electricity for the same cooling. It replaced the older SEER rating, which used an easier test.
Quick facts
The key facts about SEER2, with sources:
- Measures
- Seasonal cooling output ÷ electricity used (BTU per watt-hour) 1
- Federal minimum, split AC (North)
- 13.4 SEER2 1
- Federal minimum, split AC (Southeast and Southwest)
- 14.3 SEER2 under 45,000 BTU/h; 13.8 at 45,000 and up 1
- Federal minimum, split heat pump
- 14.3 SEER2, nationwide 1
- ENERGY STAR heat pump threshold
- 15.2 SEER2 or higher 3
- Replaced
- SEER, measured under Appendix M (2015–2022 minimums 13 and 14 SEER) 1
Key takeaways
- SEER2 tells you how much cooling a system gives per unit of electricity over a whole season. Higher is better.
- It replaced SEER on 1 January 2023. The new test pushes air through more duct resistance, so the same unit scores lower 2.
- The federal floor depends on where the system is installed: 13.4 SEER2 for a split AC in the North, 14.3 in the South 1.
- A SEER2 number only applies to the exact outdoor and indoor pairing listed in the AHRI Directory 5.
- SEER2 says nothing about heating, humidity control, noise or how well the ducts and install are done.
What SEER2 means
SEER2 is a ratio. On top is the total heat an air conditioner removes from your home across a model cooling season, counted in British thermal units (BTUs).
On the bottom is the electricity it uses to do that, counted in watt-hours. A 16 SEER2 system removes 16 BTUs of heat for every watt-hour it draws.
The word "seasonal" matters. The test does not just run the unit flat out on a hot day.
It runs it at several outdoor temperatures and part-load conditions, then weights the results to stand in for a full summer.
That is why SEER2 is the number the federal government uses to set minimum standards for central air conditioners and heat pumps 1.
The "2" marks the test. Federal rules now require SEER2 to be measured under Appendix M1 to subpart B of 10 CFR part 430, and rounded to the nearest 0.025 BTU per watt-hour 2. Before 2023, makers rated the same products under Appendix M and called the result SEER.
How a SEER2 rating is produced
- Maker pairs an outdoor unit with an indoor coil or air handler → one "combination"
- Lab runs the pair at set outdoor temperatures and part loads (Appendix M1) → cooling and watts recorded
- Fan works against 0.50 in. of water column for a conventional ducted system → more fan power counted
- Results weighted into one seasonal figure → rounded to 0.025
- Maker certifies the number to DOE → listed for that exact pair in the AHRI Directory
SEER vs SEER2: what the 2023 M1 test changed
Old SEER and new SEER2 measure the same thing. The difference is how hard the test makes the blower work. Real ducts push back on the fan. Engineers call that push-back external static pressure, measured in inches of water column.
Under the old Appendix M test, a ducted unit only had to work against 0.10 to 0.20 inches, depending on its size 2.
Under Appendix M1, a conventional ducted system must work against 0.50 inches 2. That is much closer to what a fan sees in a real house.
More resistance means the fan uses more power, so the measured efficiency drops.
The result: the same piece of equipment gets a lower number as SEER2 than it did as SEER. There is no single official conversion factor. Each combination was retested and recertified. So do not multiply an old SEER by a fixed number and treat it as a SEER2 rating; look up the listed value instead.
Federal minimums moved at the same time. From 2015 to 2022 the floor was 13 SEER for a split air conditioner in the North and 14 SEER in the Southeast and Southwest.
From 1 January 2023 it is 13.4 SEER2 and 14.3 SEER2 1. The new numbers look only slightly higher, but because the test is tougher, the real bar went up.
Federal SEER2 minimums by product type
| Product | National minimum (made from 1 Jan 2023) | Southeast / Southwest (installed from 1 Jan 2023) |
|---|---|---|
| Split AC, under 45,000 BTU/h | 13.4 SEER2 | 14.3 SEER2 |
| Split AC, 45,000 BTU/h and up | 13.4 SEER2 | 13.8 SEER2 |
| Split heat pump | 14.3 SEER2 (plus 7.5 HSPF2) | No regional SEER2 rule; national floor applies |
| Packaged AC | 13.4 SEER2 | Southwest adds 10.6 EER2 |
| Packaged heat pump | 13.4 SEER2 (plus 6.7 HSPF2) | National floor applies |
| Small-duct, high-velocity | 12 SEER2 | National floor applies |
The four ratings on one chart: what each can and cannot tell you
| Rating | Answers this question | Measured how | It cannot tell you |
|---|---|---|---|
| SEER2 (this page) | How much cooling per watt-hour over a whole summer? | Several outdoor temperatures, part loads, 0.50 in. duct resistance | Peak-heat performance, humidity removal, heating, your duct losses |
| EER2 | How efficient is it at 95°F, full blast? | One steady test at 95°F outdoors | Mild-day or part-load savings; heating |
| HSPF2 | How efficient is a heat pump over a heating season? | Several cold-weather points, weighted for a moderate climate | Output and efficiency below about 17°F; cooling |
| AFUE | What share of fuel becomes heat in a furnace or boiler? | Annual heat out ÷ fuel in, at the appliance | Duct losses, electricity used by the blower, cooling |
Example: what a SEER2 step is worth in kilowatt-hours
Take a 3-ton system (36,000 BTU/h) that runs the equivalent of 1,500 full-load hours a year. The hours are an example input, not a measurement; use your own from the SEER2 savings calculator.
Seasonal cooling = 36,000 × 1,500 = 54 million BTU. Electricity price: the US residential average of 18.31 cents per kWh for July 2026 4.
| SEER2 | Math | kWh a year | Energy cost at 18.31¢ |
|---|---|---|---|
| 13.4 (North floor) | 54,000,000 ÷ (13.4 × 1,000) | 4,030 | about $738 |
| 14.3 (South floor) | 54,000,000 ÷ (14.3 × 1,000) | 3,776 | about $691 |
| 16.0 | 54,000,000 ÷ (16.0 × 1,000) | 3,375 | about $618 |
| 18.0 | 54,000,000 ÷ (18.0 × 1,000) | 3,000 | about $549 |
Each step up saves less than the one before, because you divide by a bigger number. Going from 13.4 to 16 cuts about 655 kWh in this example; going from 16 to 18 cuts about 375 kWh.
In a hot, long cooling season the hours rise and so do the savings. In a short one, the gap may never repay a higher-rated unit. Equipment prices are not shown here; see what drives HVAC cost.
Where you will see SEER2
- On the yellow EnergyGuide label on the outdoor unit. The FTC requires efficiency ratings on new central air conditioners and heat pumps 9.
- On the AHRI certificate for your exact outdoor unit, indoor coil and furnace or air handler. This is the number that counts for rebates 5.
- On a contractor quote, usually beside the tonnage. Ask for the AHRI reference number so you can check it.
- On a rebate form. Most utility and state programs set a SEER2 floor; check yours on the rebate finder.
- On older paperwork as SEER. A system made before 2023 will show SEER only. Do not compare that figure head to head with a new SEER2 quote.
Why SEER2 is useful
What it does well
- One number that lets you compare cooling efficiency across brands, tested the same way.
- A tougher, more realistic duct test than old SEER, so the rating is closer to what a real house sees.
- The basis for federal minimums, ENERGY STAR and most rebates, so it is easy to check.
- Lets you estimate yearly cooling kWh with simple math, as shown above.
Where it falls short
- Tested in a lab, with set temperatures. Your attic ducts and your summer are different.
- A single average. Two units with the same SEER2 can behave very differently at 105°F.
- Does not cover moisture removal, noise or heating.
- Valid only for the listed pairing. Swap the indoor coil and the rating can change.
What SEER2 cannot tell you
The rating describes the equipment, not the installed system. A federal lab study by NIST found that duct leakage, low refrigerant charge, undersized ducts and low indoor airflow are the installation faults most likely to raise a heat pump’s yearly energy use 7.
None of those show up on the label. A 17 SEER2 unit on leaky, undersized ducts can use more power than a well-installed 15.
SEER2 also assumes a set duct resistance of 0.50 inches for conventional ducted systems 2. Many homes run higher. If your ducts are tight or undersized, the fan works harder than the test assumed.
Finally, SEER2 is weighted toward mild and moderate days. In the desert Southwest, where many hours sit above 100°F, the peak-heat rating, EER2, can matter as much.
How SEER2 affects cost and lifespan
Higher SEER2 usually comes from more hardware: a bigger outdoor coil, a two-stage or variable-speed compressor, and a variable-speed indoor fan. Those parts raise the purchase price, and on some models the repair bill. A single-stage unit at the federal floor has the fewest parts.
SEER2 does not predict how long a system lasts. Lifespan depends more on install quality, climate, salt air and upkeep. See the evidence in our equipment lifespan review.
HyreHVAC does not publish dollar figures for equipment until enough dated quotes support them. To see what moves the price, use the replacement cost calculator.
How to check a SEER2 rating on a quote
- Ask the contractor for the model numbers of the outdoor unit, the indoor coil or air handler, and the furnace if there is one.
- Ask for the AHRI certified reference number for that exact pairing.
- Look the number up in the AHRI Directory and confirm the SEER2, EER2 and (for heat pumps) HSPF2 5.
- Check the rating against your region’s minimum and against any rebate floor.
- Confirm the quote includes a load calculation, so the tonnage fits the house. A high SEER2 does not fix a wrong size.
A licensed contractor does the install, permit and start-up. Only an EPA Section 608 certified technician may handle refrigerant.
Keeping real-world efficiency close to the rating
- Check the air filter monthly and change it when dirty. ENERGY STAR advises a monthly look 8.
- Keep 2 feet of open space around the outdoor unit. Rinse off grass and cottonwood fluff from the outside of the coil, power off first.
- Book a spring check. A technician cleans the coils, checks refrigerant charge and fan airflow 8.
- Keep supply and return vents open. Closing rooms adds duct resistance.
Sources: [8]
Warning signs and when to call a pro
- Your summer bills climb year over year with no change in use. Efficiency is slipping, often from a dirty coil or low charge.
- The system runs nonstop on a mild day, or short-cycles on and off.
- Ice on the indoor coil or the copper suction line. Turn the system off and call; do not chip ice.
- A quote lists SEER2 without an AHRI number, or quotes an old SEER figure for a new unit.
- Refrigerant work, electrical repairs and coil replacement are for licensed, EPA 608 certified technicians only.
The rules behind SEER2
The U.S. Department of Energy sets the standards in 10 CFR 430.32(c). National minimums apply by date of manufacture. Regional minimums for air conditioners apply by date of installation, and the rule says a model rated below the regional level "cannot be installed in that region" 1.
The test is Appendix M1 to subpart B of 10 CFR part 430, mandatory since 1 January 2023 2. Industry standard AHRI 210/240 sets the matching rating method used by manufacturers 6.
ENERGY STAR is voluntary. Its current heat pump criteria call for at least 15.2 SEER2, 11.0 EER2 and 7.8 HSPF2 for split systems 3. For the regional map and the full state list, see our regional SEER2 research.
Common SEER and SEER2 misconceptions
- Myth A 14.3 SEER2 unit is less efficient than an old 15 SEER unit.
- Reality Not necessarily. The numbers come from different tests. Compare SEER2 to SEER2 only.
- Myth You can convert SEER to SEER2 with one fixed factor.
- Reality There is no official factor. Each pairing was retested; use the listed figure.
- Myth Higher SEER2 always pays for itself.
- Reality Only with enough cooling hours. In mild climates the yearly kWh gap is small, as the example shows.
- Myth The outdoor unit has one SEER2 number.
- Reality The rating belongs to a matched outdoor and indoor pair. Change the coil and the number can change.
- Myth After 2023 old SEER systems must be replaced.
- Reality No. The rules cover new equipment. An existing system can keep running and be repaired.
Your region sets the floor
SEER2 is the one rating where geography is written into federal law.
If you live in a Southeast state such as Florida, Georgia, North Carolina or Texas, a new split air conditioner under 45,000 BTU/h must reach 14.3 SEER2.
In the Southwest (Arizona, California, Nevada, New Mexico), it must also clear an EER2 floor for peak heat. Northern states such as Ohio and Washington use the 13.4 national floor 1.
Long, hot seasons also raise the payback from a higher rating; check your cooling degree days.
How much SEER2 do you need?
Start with the legal floor for your region, then add efficiency only where your cooling hours justify it.
A useful rule: in a long, hot season, compare quotes a few SEER2 points apart with the example math above.
In a short, mild one, put the money into ducts, sizing and install quality first, since those losses are not in the rating.
If you also heat with the system, read HSPF2 beside SEER2. If you live where summers top 100°F, read EER2 too.
Next step: run your own numbers in the energy savings calculator, then compare units on our air conditioner shortlist.
Questions about SEER2
What is a good SEER2 rating?
A good SEER2 rating is one that clears your region’s legal minimum and fits your cooling hours. The floor for a new split air conditioner is 13.4 SEER2 in the North and 14.3 in the South.
ENERGY STAR heat pumps start at 15.2. In hot, long seasons, 16 to 18 is often worth pricing. In mild climates, the extra savings are small, so ducts and install quality may matter more.
Is SEER2 the same as SEER?
No. SEER2 measures the same idea, seasonal cooling per watt-hour, but under the tougher Appendix M1 test that started on 1 January 2023. The new test makes the blower push against 0.50 inches of duct resistance instead of 0.10 to 0.20. That lowers the number for the same equipment. Compare SEER2 only with SEER2.
How do I convert SEER to SEER2?
You cannot convert it reliably. DOE did not publish a single factor, because the drop depends on the unit’s fan and design. Every product sold since 2023 was retested.
Look up the SEER2 for the exact model pairing in the AHRI Directory. Many charts online quote a rough ratio, but treat that as a guess, not a rating.
What is the minimum SEER2 in 2026?
In 2026 the federal minimum for a new split air conditioner is 13.4 SEER2 in Northern states and 14.3 SEER2 in the Southeast and Southwest for units under 45,000 BTU/h. Split heat pumps need 14.3 SEER2 everywhere.
These levels have applied since 1 January 2023 under 10 CFR 430.32. Check the eCFR before relying on them, as the rule can be amended.
Is a higher SEER2 always worth it?
No. Each step up saves fewer kWh than the step before. In our 3-ton example, going from 13.4 to 16 SEER2 saves about 655 kWh a year, but 16 to 18 saves about 375.
If you cool only a few hundred hours a year, the extra cost may never come back. Run your hours and power price before paying for the top rating.
Can I install an old SEER unit in 2026?
Only if it meets the current standard where you install it. In the South, a split air conditioner rated below the regional SEER2 level cannot legally be installed.
In the North, the national standard is based on when it was made. A contractor can tell you if leftover stock qualifies. Repairs on your existing system are not affected.
Does SEER2 apply to heat pumps?
Yes. A heat pump has a SEER2 rating for cooling and an HSPF2 rating for heating. The federal floor for a split heat pump is 14.3 SEER2 and 7.5 HSPF2. If you rely on the heat pump in winter, HSPF2, and its cold-weather output, can matter more than the cooling number.
Where do I find my system’s SEER2?
Look at the yellow EnergyGuide label on the outdoor unit, or the AHRI certificate from your installer. The AHRI Directory lists the rating for each matched outdoor and indoor pair.
If your system was made before 2023, you will find only a SEER figure. The model number on the outdoor unit’s data plate lets you look it up.
Does SEER2 tell me how well a system removes humidity?
No. SEER2 counts total cooling, which mixes temperature drop and moisture removal. A unit can score well and still leave a humid house, especially if it is oversized and runs in short bursts. Ask about the sensible heat ratio, variable-speed fans and a dehumidify mode if humidity is your main complaint.
Why did my new system’s rating look lower than my old one?
Because the old one was probably rated in SEER and the new one in SEER2. The 2023 test assumes more duct resistance, which lowers the number. A new 14.3 SEER2 system can use the same or less power than an older system with a higher SEER label. The test changed, not the physics.
Sources
- eCFR, 10 CFR 430.32 Energy and water conservation standards and their compliance dates (current text), retrieved .
- GovInfo, 10 CFR part 430 (2024 annual edition), subpart B appendices M and M1 test procedures, retrieved .
- ENERGY STAR, Air-Source Heat Pumps key product criteria, retrieved .
- U.S. EIA, Electric Power Monthly, Table 5.6.A Average price of electricity by state, July 2026 and 2025, retrieved .
- AHRI Directory of Certified Product Performance, retrieved .
- AHRI Standard 210/240, Performance Rating of Unitary Air-conditioning and Air-source Heat Pump Equipment, retrieved .
- NIST Technical Note 1848, Sensitivity Analysis of Installation Faults on Heat Pump Performance (Domanski, Henderson, Payne, 2014), retrieved .
- ENERGY STAR, Maintenance Checklist for heating and cooling, retrieved .
- eCFR, 16 CFR part 305, FTC Energy Labeling Rule, retrieved .
Expert review
Written by the HyreHVAC Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Minimums read from the current eCFR text of 10 CFR 430.32 and the 2024 CFR edition of Appendices M and M1; ENERGY STAR criteria from its key product criteria page; electricity price from EIA Table 5.6.A. Example hours are a labelled input.
Suggest a correction. We fix errors and say what changed.