SEER vs SEER2 Difference: Why Ducted Units Rate 5% Lower

The short answer

SEER2 is the cooling efficiency rating that replaced SEER in 2023: it measures the same thing (cooling per watt of electricity) under more realistic test conditions, so the same ducted equipment rates about 4–5% lower than it did under SEER. A 17 SEER ducted unit from 2022 is roughly a 16 SEER2 unit in 2026. Higher number = more efficient = lower power bill.

In this guide

The difference between SEER and SEER2
Why the rating changed to SEER2
The conversion cheat sheet
What this means for your power bill
When the higher tier is worth it
When the higher tier is not worth it
The bottom line
Questions homeowners ask

The difference between SEER and SEER2.

SEER (Seasonal Energy Efficiency Ratio) is cooling output in BTUs divided by electrical input in watt-hours over a typical cooling season, and SEER2 is the same ratio under the 2023 test. A higher SEER means more cooling per watt of electricity, which means a lower utility bill.

A 14 SEER system produces 14 BTU of cooling for every watt-hour it draws. A 20 SEER system produces 20 BTU per watt-hour. For the same cooling load, the 20-SEER system uses about 30% less electricity.

Why the rating changed to SEER2.

The rating changed because the U.S. Department of Energy updated the testing procedure in January 2023. The old SEER test was run under artificially favorable conditions, with lower duct static pressure than real-world installations. Real duct systems in real houses have more airflow resistance than the test rig, which means real systems work harder and use more electricity than the rating predicted.

SEER2 corrects for this by testing at realistic static pressure. Same unit, same physics, different test. The resulting number is lower (usually by 4–5%) but it's closer to what you'll actually experience.

The conversion cheat sheet.

To convert a ducted system, subtract about 5% from an old SEER number to approximate SEER2:

14 SEER (old) ≈ 13.4 SEER2 (new)
15 SEER ≈ 14.3 SEER2
16 SEER ≈ 15.2 SEER2
17 SEER ≈ 16.2 SEER2
18 SEER ≈ 17.1 SEER2
20 SEER ≈ 19.0 SEER2

SEER vs SEER2 conversion for ducted equipment: 14 SEER is about 13.4 SEER2, 15 is 14.3, 16 is 15.2, 17 is 16.2, 18 is 17.1 and 20 is 19.0, about 4 to 5% lower under the new test. — Same ducted equipment, different test conditions: SEER2 numbers run about 4 to 5% lower than the old SEER for identical units.

What this means for your power bill.

A higher SEER2 tier changes a Vancouver power bill very little. SEER2 rates cooling only, and Vancouver doesn't cool enough hours per year for big savings.

When the higher tier is worth it.

A higher SEER2 tier is worth it mainly for comfort. Higher-tier units are usually two-stage or variable-speed, which run longer at lower output: more even temperatures, better humidity control and less noise.

When the higher tier is not worth it.

A higher SEER2 tier is not worth it when something else limits the system:

Your ductwork is bad. Leaky ducts lose conditioned air before it reaches the rooms, and a higher SEER2 rating does not fix that. Fix the ducts first.
You already oversized. A 5-ton unit on a 3-ton load cycles too short to benefit from efficiency features. Sizing matters more than SEER2.

Real talk on marketing numbers

Manufacturers sometimes publish a single high SEER2 rating for a product line, but that rating only applies to a specific combination of outdoor unit + indoor coil + air handler. Change any of those three, and the real SEER2 can drop. The AHRI certificate for your actual matched set is the number that counts. We pull that for every quote.

The bottom line.

SEER2 is a more honest number than the old SEER, and higher is still better. In Vancouver, a higher SEER2 tier makes the most sense for homeowners who value comfort and quiet. For a system sized to your home, with the certified SEER2 of each option, request a quote.

Questions homeowners ask.

What do SEER and SEER2 ratings actually measure?

SEER (Seasonal Energy Efficiency Ratio) is a ratio of cooling output in BTUs divided by electrical input in watt-hours over a typical cooling season; a higher SEER means more cooling per watt of electricity and a lower utility bill. SEER2 measures the same thing but uses a testing procedure the U.S. Department of Energy updated in January 2023 to reflect realistic duct static pressure. It's the same physical equipment and physics, just a more accurate number, typically about 4-5% lower than the old SEER rating for identical ducted units.

Why did the SEER rating change to SEER2?

The U.S. Department of Energy updated the testing procedure in January 2023 because the old SEER test was run under artificially favorable conditions, with lower duct static pressure than real-world installations. Real duct systems in real houses have more airflow resistance than the test rig, so actual systems work harder and use more electricity than the old rating predicted. SEER2 corrects for this by testing at realistic static pressure, the same unit and physics, just a different, more accurate test, usually producing a number 4-5% lower but closer to what homeowners actually experience.

How do you convert an old SEER rating to the new SEER2 number?

For a ducted system, the rule of thumb is to subtract about 5% from an old SEER number to approximate SEER2. Rough equivalents: 14 SEER (old) is about 13.4 SEER2; 15 SEER is about 14.3 SEER2; 16 SEER is about 15.2 SEER2; 17 SEER is about 16.2 SEER2; 18 SEER is about 17.1 SEER2; and 20 SEER is about 19.0 SEER2.

How much does a higher SEER2 rating actually save on a Vancouver power bill?

Very little. SEER2 rates cooling only, and Vancouver doesn't cool enough hours per year for big savings, so a higher SEER2 tier changes a Vancouver power bill only modestly. Comfort, humidity control and quiet are the stronger reasons to pay for a higher tier.

When is it worth paying more for a higher SEER2 tier?

Mainly for comfort. Higher-tier units are usually two-stage or variable-speed, which run longer at lower output for more even temperatures, better humidity control and less noise. The power bill savings alone are modest in Vancouver, because Vancouver doesn't cool enough hours per year for big savings.

When does upgrading to a higher SEER2 tier not make sense?

A higher SEER2 tier usually isn't worth it if your ductwork is leaky, because leaky ducts lose conditioned air before it reaches the rooms and a higher SEER2 rating does not fix that, so fixing the ducts should come first. And if the system is already oversized, a 5-ton unit on a 3-ton load cycles too short to benefit from efficiency features, so correct sizing matters more than the SEER2 number.

Sources and resources

Reviewed for accuracy by Sam Tsarenko, founder of Pacific Peak Mechanical. This guide draws on the following primary sources:

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