⚡SEER, SEER2, EER and COP — one machine, five numbers

✓ Tested & verified Updated: Aug 9, 2026 How we calculate this

Efficiency rating converter

Rating on the label

Which rating it is

12.8 EER ≈ 3.75 COP

About 16 SEER, which is 15.2 SEER2 on a ducted split system.

Electricity per ton of cooling: 0.94 kW/ton
Cooling per kilowatt drawn: 12,800 BTU/h
Running a 3-ton unit: 2.8 kW while it cools

SEER is a season average, EER is a single hot afternoon. Converting between them is an estimate by nature — the exact relationship depends on the climate the unit sits in.

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How do you convert SEER to EER?

EER = 1.12 × SEER − 0.02 × SEER². A 16 SEER unit works out at about 12.8 EER, and a 20 SEER unit at about 14.4. The relationship curves rather than scaling, because the two ratings measure different things: EER is efficiency at one hot condition — 95 °F outside — while SEER averages a whole cooling season, most of which is milder.

COP is EER in metric clothing. Divide EER by 3.412 and you have it: 12.8 EER is a COP of 3.75, meaning the unit moves 3.75 units of heat for every unit of electricity it eats. Nothing about the machine changes; only the units do.

SEER2 is not a worse machine, it is a harder test. From 2023 the US test procedure raised the external static pressure the equipment has to work against, so it now measures the unit against something closer to real ductwork. Ratings dropped by roughly 5% for ducted split systems — a 16 SEER unit became about 15.2 SEER2 without a single part changing.

The same machine, read five ways. Pick the row that matches the label you are holding.

SEER	SEER2 (ducted split)	EER	COP	kW/ton
13	12.4	11.2	3.28	1.07
14	13.3	11.8	3.46	1.02
16	15.2	12.8	3.75	0.94
18	17.1	13.7	4.01	0.88
20	19.0	14.4	4.22	0.83
24	22.8	15.4	4.51	0.78

Notice how the EER column flattens while SEER keeps climbing. That is not an artefact — the very high SEER numbers come from variable-speed equipment that is extremely efficient at part load, and part load is most of the season but not the afternoon you bought it for.

Frequently asked questions

What is 16 SEER in EER?

About 12.8 EER, or a COP of 3.75. Note that this is a conversion between a seasonal average and a peak-condition rating, so it is an estimate: the same unit in Phoenix and in Seattle has the same EER but genuinely different seasonal performance.

Is SEER2 the same as SEER?

It is the same quantity measured under a tougher test. Since 2023 US ratings are taken at a higher external static pressure — 0.5 in. w.c. instead of 0.1 for most ducted systems — which reflects real ductwork. That knocks about 5% off a ducted split system’s number. A unit rated 15 SEER2 is roughly the old 15.8 SEER.

What is a good SEER2 rating?

The US federal minimum from 2023 is 13.4 SEER2 in the north and 14.3 SEER2 in the south for split systems. Anything at 16 SEER2 or above is a high-efficiency unit. Whether the extra is worth paying for depends on how many hours a year it runs — the same upgrade pays back in three years in Texas and twenty in Maine.

How do I convert EER to COP?

Divide by 3.412. EER is BTU per hour of cooling per watt of electricity; COP is watts of cooling per watt of electricity. Since one watt is 3.412 BTU/h, the two are the same ratio expressed in different units — an EER of 10 is a COP of 2.93.

What is kW per ton and how does it relate to EER?

kW per ton is the commercial world’s version of the same ratio, inverted: kW/ton = 12 ÷ EER. A 12 EER chiller is 1.0 kW/ton. Because it is inverted, lower is better — which catches out anyone moving between residential and commercial specifications.

Does a higher SEER mean lower bills in every climate?

It means lower bills per hour of running, but the saving is proportional to hours. SEER is weighted for a season with a lot of part-load hours, so a variable-speed high-SEER unit shines in a long mild summer and matters far less in a climate with a short, brutally hot one — where the EER at 95 °F is closer to what you will actually experience.

How we calculate this

SEER to EER uses the relationship EER = 1.12 × SEER − 0.02 × SEER², the approximation long used in ASHRAE and DOE literature for translating a seasonal rating into a peak-condition one. It is an approximation by construction: SEER is a weighted seasonal average and EER is a single test point, so no exact conversion exists. EER to COP is exact: COP = EER ÷ 3.412142, since one watt equals 3.412142 BTU/h. kW per ton is 12 ÷ EER, also exact, from 12,000 BTU/h in a ton of refrigeration. SEER2 and EER2 are taken as 0.95 × SEER and 0.95 × EER, the conversion factor published by the US Department of Energy for ducted split systems under the 2023 test procedure; packaged and ductless equipment use different factors, and the only authoritative SEER2 figure is the one from re-testing.

Worked example

With Rating on the label 16, Which rating it is SEER — seasonal, pre-2023 label, this page works out 12.8 EER ≈ 3.75 COP. About 16 SEER, which is 15.2 SEER2 on a ducted split system.

Electricity per ton of cooling0.94 kW/ton
Cooling per kilowatt drawn12,800 BTU/h
Running a 3-ton unit2.8 kW while it cools

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