SEER2 is the number that tells you how efficiently a new air conditioner or heat pump cools your home: the higher it is, the less electricity the system needs to keep you comfortable. Since January 1, 2023, every new central AC and heat pump sold in the U.S. is rated in SEER2 instead of the older SEER.
If you’re shopping for a replacement system, understanding this one rating will help you compare quotes, meet local requirements, and estimate what you’ll spend on cooling for the next 15 years.
What does SEER mean?
SEER stands for Seasonal Energy Efficiency Ratio. It is the total cooling a system delivers over a typical cooling season, divided by the electricity it uses to do it.
The test holds the indoor temperature steady while outdoor temperatures range from 65°F to 104°F, which simulates a full season rather than a single hot afternoon (Trane).
Think of it like a car’s combined miles-per-gallon. A car does better on the highway and worse in the city; the combined figure is the average. SEER works the same way: your system may run more or less efficiently on a given day, but the rating is its seasonal average (American Standard).
What is SEER2, and why did it replace SEER?
SEER2 is the same idea as SEER, measured under a tougher, more realistic test. The U.S. Department of Energy made it the official standard for equipment manufactured on or after January 1, 2023.
The key change is the DOE’s new M1 test procedure. Real homes have ductwork, filters and coils the blower has to push air through, and the old test underestimated that resistance. M1 raises the external static pressure in the test by a factor of five to better match an installed system (Trane; Federal Register).
Because the test is harder, the same equipment scores a little lower in SEER2 than it did in SEER. That isn’t a downgrade; it’s a more honest estimate of what you’ll get at home. EER became EER2 and HSPF became HSPF2 at the same time.
Converting SEER to SEER2
To estimate a ducted system’s SEER2 from its old SEER rating, divide by 1.05. Ductless mini-splits keep roughly the same number, because the M1 change mainly affects systems that push air through ducts (American Standard).
| Old SEER | Ducted SEER2 | Ductless SEER2 |
|---|---|---|
| 14 | 13.4 | 14 |
| 15 | 14.3 | 15 |
| 16 | 15.2 | 16 |
| 17 | 16.2 | 17 |
| 18 | 17.2 | 18 |
| 20 | 19 | 20 |
Today’s minimum SEER2 by region
The DOE sets minimum efficiency by region. The Southeast covers hot-humid states including Florida, Georgia, Texas, Alabama, the Carolinas, Tennessee and Virginia; the Southwest is Arizona, California, Nevada and New Mexico; everything else is the North (DOE 2023 standards FAQ).
| Equipment (new since Jan 1, 2023) | North | Southeast | Southwest |
|---|---|---|---|
| Split AC, under 45,000 Btu/h | 13.4 SEER2 | 14.3 SEER2 | 14.3 SEER2 + 11.7 EER2* |
| Split AC, 45,000 Btu/h or more | 13.4 SEER2 | 13.8 SEER2 | 13.8 SEER2 + 11.2 EER2* |
| Split heat pump | 14.3 / 7.5 HSPF2 | 14.3 / 7.5 HSPF2 | 14.3 / 7.5 HSPF2 |
| Packaged AC | 13.4 SEER2 | 13.4 SEER2 | 13.4 SEER2 + 10.6 EER2 |
| Packaged heat pump | 13.4 / 6.7 HSPF2 | 13.4 / 6.7 HSPF2 | 13.4 / 6.7 HSPF2 |
*Drops to 9.8 EER2 for systems rated 15.2 SEER2 or higher. Heat pump cells show SEER2 / HSPF2.
In the Southeast and Southwest, the AC rule is based on the installation date, so a contractor cannot legally install a split AC below the regional minimum, even old stock. In the North, the rule is based on the manufacture date.
What’s a good SEER2 rating?
For most homes, 15 to 17 SEER2 is a strong, cost-effective target, and 18+ SEER2 makes sense where summers are long and hot. The best rating depends on your climate, how long you’ll stay in the home, and your budget (Trane).
SEER2 rises with the type of compressor inside the unit, so the rating also tells you a lot about how the system runs:
| SEER2 range | Typical compressor | How it runs | Best fit |
|---|---|---|---|
| 13.4–15 | Single-stage | On at 100% or off; cycles frequently | Mild or short summers, lower budget, shorter stay |
| 15–17 | Two-stage or multi-stage | Runs on low most days, high on the hottest | Most homes; good balance of cost and savings |
| 17–24 | Variable-speed | Adjusts output (e.g. 30–100%) in long, steady cycles | Long, hot, humid summers; best comfort and humidity control |
Ranges reflect current Trane and American Standard product lines; Trane’s single-stage units run 13–17 SEER2 and its variable-speed units 17–24 SEER2.
For perspective, air conditioners and heat pumps built 10 to 15 years ago typically rated only 8 to 10 SEER. Even an entry-level SEER2 system today is a large step up.
For Tampa Bay and the rest of Florida: the legal floor for a new split AC is already 14.3 SEER2, and cooling runs most of the year. That long season is exactly where a 16–18+ SEER2 two-stage or variable-speed system earns back its higher price fastest, and where better humidity control matters most.
Is a higher SEER2 rating worth it?
Usually yes, if you run your AC for much of the year: a higher-SEER2 system costs more up front but uses less electricity for its entire 15-year-or-so life. Trane notes an 18 SEER2 unit is about 20% more efficient than a 14 SEER2 single-stage unit, and a 20 SEER2 unit about 43% more efficient (Trane).
To estimate the cut in cooling electricity yourself, compare the two ratings:
Going from 14 to 20 SEER2 cuts cooling energy by about 1 − 14/20 = 30%. Replacing a 10 SEER system (about 9.5 SEER2) with a 16 SEER2 system cuts it by about 40%. That lines up with American Standard’s estimate that replacing an AC or heat pump 10+ years old could save 20–40% on energy costs each year (American Standard). If your cooling costs $1,000 a year, 30% is roughly $300 a year, or about $4,500 over 15 years before rate increases.
What you gain
- Lower bills for the life of the system
- Better comfort: long, low-speed cycles keep temperatures even
- Better humidity control in humid climates
- Quieter operation than a single-stage unit cycling at full blast
What to weigh
- Higher upfront price
- Slower payback where summers are short and mild
- Less value if you plan to move within a few years
What else affects real-world efficiency
A high rating is not the whole story. Your installed results also depend on:
- Correct sizing: An oversized unit short-cycles and wastes its rating. Ask for a load calculation.
- Ductwork and insulation: Leaky ducts or a poorly insulated attic erase efficiency gains.
- A matched system: The rating assumes a properly paired indoor coil or air handler, which is why listings say “up to.”
- Installation and maintenance: Correct refrigerant charge, airflow and regular filter changes keep the system near its rating.
SEER2’s companion ratings: EER2, HSPF2 and ENERGY STAR
SEER2 measures average cooling efficiency, but two other ratings fill in the picture (Trane; DOE):
| Rating | What it measures | Test conditions | Why it matters |
|---|---|---|---|
| SEER2 | Average cooling efficiency over a season | Outdoor 65°F–104°F | Overall cooling cost |
| EER2 | Cooling efficiency at peak load | 95°F outdoor, 80°F indoor, 50% humidity | Performance on the hottest days |
| HSPF2 | Heat pump heating efficiency over a season | Winter heating season | Heating cost (heat pumps only) |
ENERGY STAR certification sets a bar above the federal minimum. Split heat pumps need at least 16 SEER2 plus EER2 and HSPF2 minimums; packaged heat pumps need at least 15.2 SEER2 (American Standard).
Incentives in 2026: the federal 25C tax credit for efficient heat pumps and ACs ended for equipment installed after December 31, 2025, so 2026 installs no longer qualify (Trane). Utility rebates, manufacturer promotions and state-run heat pump rebate programs may still apply; those funded under the Inflation Reduction Act generally require at least 16 SEER2 for split ducted heat pumps and 15.2 SEER2 for packaged units. Ask your contractor what’s available locally.
Frequently asked questions
Is SEER2 lower than SEER for the same unit?
Yes. Because the M1 test is tougher, a ducted system’s SEER2 is about 5% lower than its old SEER. A 16 SEER system is roughly 15.2 SEER2.
Do I have to replace my old SEER-rated system?
No. The standards apply to new equipment. Your existing system can keep running; the rules apply when you replace it.
Where do I find my unit’s rating?
Check the yellow EnergyGuide label on the outdoor unit, the paperwork on the indoor air handler or furnace, or contact the manufacturer with the model and serial number.
What’s the minimum SEER2 in Florida?
Florida is in the DOE’s Southeast region: 14.3 SEER2 for split ACs under 45,000 Btu/h, 13.8 SEER2 for larger split ACs, and 14.3 SEER2 for split heat pumps.
Does “up to” in a SEER2 rating mean I’ll get that number?
Not automatically. The top figure assumes the right matched indoor unit and ideal conditions; your installed result depends on the match, ductwork and installation.
The bottom line
SEER2 is the current, more realistic version of SEER: a seasonal average of how much cooling you get per unit of electricity. Every new system must meet your region’s minimum, but going higher buys lower bills, better humidity control and quieter comfort. Have a qualified HVAC contractor size the system correctly and recommend a SEER2 level that fits your climate, home and budget.
Sources
- Trane — What’s a Good SEER2 Rating? (Oct 7, 2026)
- American Standard — What is SEER? (updated Feb 2, 2026)
- U.S. Department of Energy — 2023 Central Air Conditioner Standards FAQ
- Federal Register — Test Procedure for Central Air Conditioners and Heat Pumps
- Trane — Federal Tax Credits for Energy Efficiency