SEER2 is the number on every new central air conditioner and heat pump that tells you how much cooling you get per unit of electricity. It replaced the older SEER rating in 2023, which is why the same equipment now shows a smaller number than it used to.
SEER2 is a season's cooling output in BTU divided by the electricity used in watt-hours. Higher is more efficient: a 3-ton system at 14.3 SEER2 costs about $680 a year to run at 1,500 full-load hours and 18 cents per kWh, and one at 20 SEER2 about $486. The federal minimum for split air conditioners is 13.4 SEER2 in the North and 14.3 in the South and Southwest.
What SEER2 measures
SEER2 stands for Seasonal Energy Efficiency Ratio 2. It's measured in a federal test that runs the system at several outdoor temperatures and loads, then weights the results to represent a cooling season. A higher number means more cooling for the same electricity.
Why SEER2 replaced SEER
Starting January 1, 2023, the federal test procedure changed to use higher external static pressure, closer to the resistance of real ductwork. Because the equipment works harder in the test, the same system scores lower: SEER2 reads roughly 5% below the old SEER for ducted split systems. Compare ratings in the same system; our SEER to SEER2 conversion covers the details.
Federal minimums
- Split air conditioners: 13.4 SEER2 in the North. In the South and Southwest, 14.3 SEER2 below 45,000 BTU per hour and 13.8 at 45,000 and above. The Southwest also sets a minimum EER2, a rating at a single hot test condition.
- Split heat pumps: 14.3 SEER2 and 7.5 HSPF2 nationally.
- ENERGY STAR split heat pumps: at least 15.2 SEER2, 7.8 HSPF2 and 11.0 EER2.
See minimum SEER2 by state for which states fall in each region.
What each rating costs to run
A 3-ton system at 1,500 full-load cooling hours and 18 cents per kWh:
| SEER2 | Cost per year |
|---|---|
| 13.4 | $725 |
| 14.3 | $680 |
| 16 | $608 |
| 20 | $486 |
Annual cost = tons × 12,000 × hours ÷ (SEER2 × 1,000) × rate. Each step up saves less than the last, so the right rating depends on your climate's cooling hours and the price difference; the calculator below and our SEER2 comparison calculator run it with your numbers.
SEER2 Energy Savings Calculator
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What counts as a good SEER2 rating
A good rating sits at or near 15.2 SEER2, the ENERGY STAR level for heat pumps. That is comfortably above the federal minimum for your region. The tiers below anchor to the federal and ENERGY STAR levels, and the cost column uses the same 3-ton system at 1,500 full-load hours and 18 cents per kWh as above.
| SEER2 | Where it sits | Annual cost |
|---|---|---|
| 13.4 | Federal minimum, North | $725 |
| 14.3 | Federal minimum, South and Southwest | $680 |
| 15.2 | ENERGY STAR level | $639 |
| 16 | Standard step up | $608 |
| 18 | High efficiency | $540 |
| 20 | High efficiency | $486 |
| 22 | Premium | $442 |
| 24 | Premium | $405 |
Each 2-point step buys a smaller dollar saving than the one before, because running cost falls as one divided by the rating. Going from 16 to 18 saves about $68 a year here ($608 minus $540), while the same 2-point jump from 22 to 24 saves about $37 ($442 minus $405), roughly half as much.
SEER2 by equipment type
SEER2 labels central split systems, single-packaged units, and ductless mini splits. Room units use a different metric, so a window unit's rating does not compare directly with a central system's.
- Central split systems: federal minimum 13.4 SEER2 in the North, 14.3 in the South and Southwest, dropping to 13.8 for units of 45,000 BTU per hour and above in those two regions.
- Single-packaged units (compressor and air handler in one cabinet): a uniform 13.4 SEER2 minimum nationwide, lower than split systems by design. See minimum SEER2 by state.
- Ductless mini splits: rated in SEER2 as well. Because they have no duct runs, they avoid the duct air losses the DOE puts at about 30% of a cooling system's energy.
- Window, portable, and through-the-wall units: rated in CEER or EER, a single hot-condition measure rather than a seasonal one, so they are not directly comparable with SEER2. See air conditioner types.
Where high ratings come from
The highest SEER2 ratings usually come from variable-speed or two-stage compressors and fans. They run at low speed most of the time, which is more efficient than cycling on and off at full power, and removes more humidity along the way. They cost more up front, which is the trade-off the payback math weighs.
When a higher rating pays back
Payback is the install-price difference divided by the yearly saving. Take the jump from 14.3 to 18 SEER2 on the 3-ton example: the cost falls from $680 to $540 a year, a saving of $140 at 1,500 full-load hours.
Suppose the higher-rated system costs $1,200 more to install, an example figure since prices vary. Dividing $1,200 by $140 gives a payback of about 8.6 years at 1,500 hours.
Cooling hours drive that payback, and they rise from the northern states to the Deep South. The same 14.3-to-18 jump saves about $75 a year at 800 hours, $140 at 1,500, and $233 at 2,500, all on the 3-ton system at 18 cents per kWh.
Each figure is the annual-cost formula run at that hour count: 3 × 12,000 × hours ÷ (14.3 × 1,000) minus the same at 18, times 18 cents. With the $1,200 example difference, payback runs about 16 years at 800 hours, 8.6 at 1,500, and 5.2 at 2,500, which is why a long southern season justifies a higher rating and a short northern one often does not.
Myths to ignore
- "A higher SEER2 means a smaller unit." No. SEER2 is efficiency; tonnage is capacity. Size the system first, then choose the rating.
- "SEER and SEER2 are the same." They come from different tests. An old 16 SEER unit is about 15.2 SEER2.
- "The rating guarantees the savings." Installation and ducts matter. The DOE puts duct air losses at about 30% of a cooling system's energy, and a poorly installed system won't reach its rating.
Frequently asked questions
What is a good SEER2 rating?
Anything at or above the minimum works; 15 to 17 SEER2 is a common middle ground. Higher ratings pay back faster in hot climates with long cooling seasons.
What is the minimum SEER2 in 2026?
13.4 SEER2 for split air conditioners in the North, and 14.3 in the South and Southwest for systems below 45,000 BTU per hour (13.8 at 45,000 and above).
How do I convert SEER to SEER2?
Roughly multiply by 0.95 for a ducted split system. A 14 SEER unit is about 13.3 SEER2.
Does SEER2 apply to heat pumps?
Yes, for cooling. Heat pumps also carry an HSPF2 rating for heating.
Sources & References
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