If you have shopped for a new air conditioner or heat pump recently, you have probably noticed that efficiency ratings now use “SEER2” instead of the old “SEER” system. This change has created confusion for homeowners trying to compare systems. Here is everything you need to know about what changed, why, and what it means for you.
Quick Comparison: SEER vs SEER2
| Feature | SEER (Old) | SEER2 (New) |
|---|---|---|
| Effective date | Pre-2023 | January 1, 2023+ |
| Test procedure | ARI 210/240 | AHRI 210/240 with M1 procedure |
| External static pressure | 0.1” w.c. | 0.5” w.c. (5x higher) |
| Cycling losses measured? | No | Yes |
| Numbers | Higher | 4-7% lower for same equipment |
| Minimum (South) | 14 SEER | 13.4 SEER2 |
| Minimum (North) | 13 SEER | 13.4 SEER2 |
| What changed physically? | Nothing | Testing method only |
What Is SEER?
SEER stands for Seasonal Energy Efficiency Ratio. It measures how efficiently an air conditioner or heat pump cools over an entire cooling season. The calculation divides the total cooling output (in BTUs) by the total electrical energy consumed (in watt-hours) over a typical season.
Higher SEER = more efficient = lower electricity bills.
SEER was the standard efficiency metric for air conditioners and heat pumps for decades. A 14 SEER unit was the federal minimum, and high-efficiency units reached 25+ SEER.
What Is SEER2?
SEER2 stands for Seasonal Energy Efficiency Ratio 2. It measures the exact same thing as SEER (seasonal cooling efficiency), but using a more rigorous testing procedure called the M1 test method.
The key difference is that SEER2 testing applies five times more external static pressure (0.5 inches of water column vs. 0.1 inches) to simulate real-world conditions. In plain language, the new test better accounts for the resistance that a typical home’s duct system creates against airflow.
What Actually Changed
The Testing Method (Not the Equipment)
This is the most important thing to understand: the equipment did not change. Only the testing method changed.
When SEER2 was introduced on January 1, 2023, manufacturers did not redesign their systems. They took the same air conditioners and heat pumps, retested them using the new M1 procedure, and assigned new model numbers with SEER2 ratings.
Because the new test is more stringent (higher static pressure), the same equipment gets a lower number under SEER2. This does not mean the equipment became less efficient. It means the rating is more honest about real-world performance.
Why SEER2 Numbers Are Lower
| Old SEER Rating | Approximate SEER2 Rating | Difference |
|---|---|---|
| 13 SEER | 12.2 SEER2 | -6.2% |
| 14 SEER | 13.4 SEER2 | -4.3% |
| 16 SEER | 15.2 SEER2 | -5.0% |
| 18 SEER | 17.0 SEER2 | -5.6% |
| 20 SEER | 18.9 SEER2 | -5.5% |
| 22 SEER | 20.7 SEER2 | -5.9% |
| 25 SEER | 23.5 SEER2 | -6.0% |
Quick conversion: Divide the old SEER rating by approximately 1.05 to get the SEER2 equivalent (this is approximate and varies slightly by system).
What SEER2 Tests That SEER Did Not
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Higher external static pressure: The M1 test applies 0.5” w.c. of external static pressure vs. 0.1” in the old test. This simulates the resistance from real ductwork, which the old test largely ignored.
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Cycling losses: When an AC turns on and off, it loses efficiency during the startup phase. SEER2 testing measures these “cycling losses” to provide a more realistic efficiency rating.
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More realistic operating conditions: The combination of higher static pressure and cycling loss measurement means SEER2 ratings more closely match what you will actually experience in your home.
Current Minimum Efficiency Standards
Federal Minimums (Effective January 1, 2023)
| Equipment Type | Region | Minimum SEER2 | Old SEER Equivalent |
|---|---|---|---|
| Central AC (split system) | South | 14.3 SEER2 | ~15 SEER |
| Central AC (split system) | North | 13.4 SEER2 | ~14 SEER |
| Heat pump (split system) | Nationwide | 14.3 SEER2 | ~15 SEER |
| Central AC (packaged) | South | 13.4 SEER2 | ~14 SEER |
| Central AC (packaged) | North | 13.4 SEER2 | ~14 SEER |
The “South” region (also called the “Southeast” or “Southwest” region) includes states in the southern half of the country. The “North” region includes states in the northern half. Check the DOE’s official map for exact regional boundaries.
Heating Efficiency (HSPF2)
Heat pumps also received a new heating efficiency metric: HSPF2 (Heating Seasonal Performance Factor 2), replacing the old HSPF.
| Old HSPF | Approximate HSPF2 | Notes |
|---|---|---|
| 8.2 HSPF | 7.5 HSPF2 | Old federal minimum |
| 8.8 HSPF | 8.1 HSPF2 | Current federal minimum |
| 10.0 HSPF | 9.2 HSPF2 | High efficiency |
| 13.0 HSPF | 12.0 HSPF2 | Premium efficiency |
Why This Matters When Shopping for a New AC
Comparing Old and New Systems
If you are replacing a system rated in SEER and shopping for a new system rated in SEER2, you cannot directly compare the numbers. A new 16 SEER2 system is actually more efficient than an old 16 SEER system because it achieved that rating under tougher testing conditions.
Example: Your old system is rated 14 SEER. A new system rated 14.3 SEER2 is roughly equivalent to 15 SEER under the old scale. So even the minimum-efficiency new system is an upgrade from your old 14 SEER unit.
What SEER2 Rating Should You Target?
| SEER2 Rating | Classification | Best For | Approx. Old SEER |
|---|---|---|---|
| 13.4 - 14.3 | Minimum efficiency | Budget buyers, mild climates | 14 - 15 |
| 15 - 16 | Good efficiency | Most homeowners | 16 - 17 |
| 17 - 19 | High efficiency | Hot climates, energy-conscious | 18 - 20 |
| 20+ | Premium efficiency | Maximum savings, hot climates | 21+ |
For most homeowners, 15 to 17 SEER2 offers the best balance of upfront cost and long-term energy savings. Systems above 20 SEER2 provide diminishing returns unless you live in a very hot climate with high electricity costs.
Use our Energy Savings Calculator to see how different SEER2 ratings affect your energy bills.
EER2: The Other Efficiency Rating
You may also see EER2 (Energy Efficiency Ratio 2) on equipment specifications. While SEER2 measures seasonal efficiency, EER2 measures efficiency at a single peak condition (95 degrees Fahrenheit outdoor temperature). EER2 is more relevant for hot climates where the system runs at full capacity for extended periods.
Common Misconceptions
”SEER2 means the equipment is less efficient”
False. The same equipment simply receives a lower number because the test is harder. A system rated 16 SEER2 performs identically to the same system that would have been rated approximately 17 SEER under the old method.
”I should buy a system with the highest SEER2 possible”
Not necessarily. Higher SEER2 ratings cost significantly more upfront. The energy savings from going from 16 SEER2 to 22 SEER2 may take 10 to 15+ years to recover in mild climates. The sweet spot for most homes is 15 to 17 SEER2.
”My old 16 SEER system is more efficient than a new 15 SEER2 system”
False. A new 15 SEER2 system is actually equivalent to approximately 16 SEER under the old testing. Plus, a new system benefits from years of engineering improvements in compressor technology, coil design, and refrigerant management.
”SEER2 only applies to new equipment”
Correct. Equipment manufactured before January 1, 2023, retains its original SEER rating. Only equipment manufactured after that date carries SEER2 ratings. You may encounter both ratings when shopping, especially if a dealer has older stock.
How SEER2 Affects Related Decisions
Compressor Type and SEER2
The compressor type is the biggest factor in achieving high SEER2 ratings:
| Compressor Type | Typical SEER2 Range | Cost Impact |
|---|---|---|
| Single-stage | 13.4 - 15 SEER2 | Lowest |
| Two-stage | 15 - 19 SEER2 | Moderate |
| Variable-speed | 17 - 26+ SEER2 | Highest |
For more details on compressor types, read our Single-Stage vs Two-Stage vs Variable-Speed comparison.
Tax Credits and SEER2
Federal tax credits through the Inflation Reduction Act require specific efficiency thresholds. For heat pumps, qualifying for the $2,000 credit typically requires meeting Energy Star’s “Most Efficient” criteria, which is updated annually. Check Energy Star’s current requirements for specific SEER2 and HSPF2 thresholds.
Ductwork and Real-World Efficiency
Ironically, the reason SEER2 exists is because of ductwork. The old SEER test essentially pretended your ducts were perfect. SEER2 acknowledges that ducts create real resistance.
This makes duct condition more important than ever. Even a high-SEER2 system will underperform if your ducts are leaky, undersized, or poorly insulated. If you are investing in a high-efficiency system, consider having your ductwork inspected and sealed. Read our Duct Cleaning Cost guide for more information.
Frequently Asked Questions
Is SEER2 better than SEER?
SEER2 is not “better” in terms of the equipment; it is a more accurate measurement. SEER2 ratings better reflect real-world performance because the testing conditions more closely match actual installed conditions. This helps consumers make more informed comparisons.
How do I convert SEER to SEER2?
Divide the SEER rating by approximately 1.05. For example, 16 SEER divided by 1.05 equals approximately 15.2 SEER2. This is an approximation since the actual conversion varies slightly by system design.
What is the minimum SEER2 rating I can buy?
As of 2023, the federal minimum for split-system air conditioners is 13.4 SEER2 in the North and 14.3 SEER2 in the South. Heat pumps must meet a minimum of 14.3 SEER2 nationwide. These minimums may increase in future regulatory updates.
Does a higher SEER2 rating always save money?
Higher SEER2 ratings always mean lower electricity consumption. However, the higher upfront cost of premium-efficiency equipment means the payback period varies. In hot climates with 6+ months of cooling, higher SEER2 pays off faster. In mild climates, a moderate SEER2 rating may be the better value.
My contractor quoted me a system with a SEER rating, not SEER2. Is that a problem?
If the system was manufactured before January 2023, it will carry a SEER rating, which is normal. If it was manufactured after January 2023, it should carry a SEER2 rating. Ask your contractor to clarify the manufacturing date and applicable rating.
In Central Texas? Texas Temp Masters can help you understand efficiency ratings and choose the right SEER2 level for your home and budget. We do not push the most expensive option; we help you find the best value. Call (817) 704-0706 for a free consultation, or visit our Air Conditioning page to see available systems.
