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If you haven’t shopped for a new air conditioner in several years, you may notice that efficiency ratings look a little different these days. Older systems were rated using SEER, but newer models carry SEER2 ratings, often with numbers like 13.4, 15.2, or 17.
SEER2 became the new efficiency standard for central air conditioners and heat pumps in 2023. It changed how the equipment is tested and how its efficiency is rated. The basic idea is still pretty simple: the higher the rating, the more efficiently the system uses electricity to cool your home.
That can mean a smaller number on your electric bill, but the difference between two SEER2 ratings doesn’t tell you exactly how much you’ll save. Before forking out more cash for a higher-efficiency system, it helps to know what those numbers actually mean for your energy use.
What Is SEER2?
SEER2 stands for Seasonal Energy Efficiency Ratio 2. It measures how much heat an air conditioner or heat pump removes from your home over a cooling season compared with the amount of electricity it uses to do the job.
The rating is expressed in British thermal units (Btu) of cooling per watt-hour of electricity. The higher the rating, the more energy-efficient the equipment is.
Now, you don’t have to whip out your calculator and dust off your algebra skills to make use of the rating.
Think of SEER2 as a way to compare the cooling efficiency of different systems. A 16 SEER2 air conditioner is more efficient than a 14 SEER2 model under the same standardized testing, so it should use less electricity to provide the same amount of cooling.
Why Did SEER Change to SEER2?
SEER has been used to rate air conditioner efficiency for decades, but the testing behind that rating didn’t fully reflect the conditions an HVAC system encounters once it’s installed in a home. So, the U.S. Department of Energy updated its testing requirements to create a more representative way to measure efficiency.
Those changes took effect January 1, 2023. Under the updated test procedure, systems are tested against greater external static pressure, which better accounts for the resistance an HVAC system has to overcome as it moves air through ductwork.
The updated test also brought a new name for the resulting efficiency rating: SEER2.
That’s why the SEER rating on an older air conditioner and the SEER2 rating on a new one don’t provide a direct apples-to-apples comparison. A system will generally receive a somewhat lower SEER2 rating than its SEER rating because it’s being tested under different conditions.
How Much Can a Higher SEER2 Rating Lower Your Energy Bills?
Throwing around SEER2 numbers probably doesn’t make much sense without a more tangible example. So, let’s put a dollar amount to potential savings.
The U.S. Department of Energy estimates the annual electricity of a 36,000 Btu central air conditioner in Northern states at:
- 13.4 SEER2: 4,581 kWh
- 15.2 SEER2: 4,038 kWh
- 23.5 SEER2: 2,612 kWh
For this example, we’ll use Michigan’s 2026 average residential electricity price, which is 21.53 cents per kWh. At that price, here’s what it’d cost to run those systems:
| System Efficiency Rating | Approximate Cost to Run per Year |
| 13.4 SEER2 | $986 |
| 15.2 SEER2 | $869 |
| 23.5 SEER2 | $562 |
Based on those numbers, you’d save about $117 per year in cooling costs by choosing a 15.2 SEER2 unit instead of a 13.4 SEER2 system. Moving from 15.2 to 23.5 SEER2 would save another $307 per year. Compared with the 13.4 SEER2 system, the 23.5 SEER2 system comes out about $424 cheaper to run each year.
Of course, these are just estimates rather than a prediction of what you’ll actually see on your own electricity bill. Your cooling costs will depend on how much your AC runs, your electricity rate, the weather, thermostat settings, and even your home itself.
Does the Highest SEER2 Rating Mean the Lowest Energy Bill?
A higher SEER2 rating can lower the amount of electricity your air conditioner uses, but buying the highest-rated system you can find doesn’t guarantee the lowest energy bill. Your actual energy bill will depend on how that system performs once it’s installed in your home.
And a handful of factors play into that, including:
- System Size: An oversize AC might cool your house fast but cycle on and off more frequently, which can hurt efficiency and humidity control.
- Ductwork: Leaky or poorly insulated ducts can lose conditioned air before it ever reaches your living space.
- Insulation and Air Sealing: A home that gains heat quickly makes your AC work harder to maintain the temperature you set.
- Thermostat Settings: Lower temperature settings and frequent adjustments can increase cooling demand and, in turn, up your energy bills.
- Summer Weather: When those hot, humid stretches hit, your AC will have to work longer and harder to keep up, regardless of your system’s SEER2 rating.
- Installation: Refrigerant charge, airflow, and installation quality can affect how efficiently your new AC performs.
So, moral of the story: A more efficient system should use less electricity for the same amount of cooling under comparable conditions. But that doesn’t mean that every homeowner with, say, a 20 SEER2 AC will have a lower electric bill than every homeowner with a 15 SEER2 system.
The rating gives you a way to compare the equipment itself, not a hard number that’ll dictate what your monthly electric bill will be.
SEER2 Energy Efficiency: Frequently Asked Questions
SEER2 ratings can feel a little confusing once you start comparing new equipment with an older system. Here are answers to a few common questions we get about current efficiency standards.
What SEER2 rating does a new AC need in Michigan?
For a standard split-system or single-package central air conditioner, the federal minimum for Michigan is 13.4 SEER2. The U.S. Department of Energy established that minimum as part of the efficiency standards that took effect at the beginning of 2023.
What is a good SEER2 rating?
A good SEER2 rating depends on what you want out of your new system. 13.4 SEER2 is the minimum you can go with for certain units, but if you want something more efficient, a higher-rated system might be your best bet.
Is SEER2 better than SEER?
SEER2 isn’t simply a higher-efficiency version of SEER. It’s an updated rating based on a newer testing procedure designed to better represent the conditions HVAC equipment encounters after installation.
How much can a higher-SEER2 AC save on electricity?
That’ll depend on the ratings you’re comparing. For example, a 15.2 SEER2 AC uses about 12% less electricity annually than a 13.4 SEER2 model. A 23.5 SEER2 model uses about 43% less. Your actual savings will depend on your cooling use, electricity rate, home, and system performance.
Do I need to replace my AC because of the new SEER2 standards?
Nope. The SEER2 standards don’t require you to replace an older air conditioner just because it was manufactured under the previous efficiency standards. If your current AC is still cooling your house properly, you can keep on using it.
The newer requirements affect the efficiency standards for equipment manufactured or installed under applicable federal rules.
Does SEER2 apply to heat pumps?
It sure does. Heat pumps get a SEER2 rating for their cooling efficiency. Since they also provide heating, you’ll see an HSPF2 rating, too, which measures seasonal heating efficiency.
Can I compare a SEER rating directly to a SEER2 rating?
No. SEER and SEER2 come from different testing procedures, so a 16 SEER system and a 16 SEER2 system aren’t being measured under exactly the same conditions. So, if you’re comparing an older AC with a new one, look at more than those two numbers alone.
Compare Your AC Replacement Options with Dynamic HVAC
There’s a pretty big efficiency range among today’s air conditioners, and the highest SEER2 rating isn’t automatically the best fit for every home or budget. The kicker is finding a system that can keep up with your cooling needs and is properly sized and installed for your home.
If it’s time to replace your AC, Dynamic HVAC can walk you through the available efficiency ratings and help you pick the one that makes sense for your home.
Contact Dynamic HVAC today to schedule an estimate for AC replacement.
Sources & References
- ENERGY STAR – “Air-Source Heat Pumps Key Product Criteria”
Outlines ENERGY STAR efficiency criteria for air-source heat pumps, including SEER2 and HSPF2 requirements for eligible equipment.
https://www.energystar.gov/products/air_source_heat_pumps/key-product-criteria - U.S. Department of Energy – “2023 Central Air Conditioners and Heat Pumps Efficiency Standards FAQs”
Explains the federal efficiency standards that took effect Jan. 1, 2023, including SEER2 requirements and regional standards for central air conditioners and heat pumps.
https://www1.eere.energy.gov/buildings/appliance_standards/pdfs/2023_CAC_Standards_FAQ_10-5-2022_Final.pdf - U.S. Department of Energy – “Purchasing Energy-Efficient Residential Central Air Conditioners”
Provides SEER2 efficiency recommendations and estimated annual energy use for residential central air conditioners, including the Northern states data used in our energy-cost comparison.
https://www.energy.gov/cmei/femp/purchasing-energy-efficient-residential-central-air-conditioners - U.S. Energy Information Administration – “Average Price of Electricity to Ultimate Customers by End-Use Sector”
Provides monthly and year-to-date residential electricity prices by state. We used Michigan’s 2026 year-to-date residential electricity price to estimate the annual operating costs in our SEER2 comparison.
https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=table_5_06_b
