What do SEER2 ratings mean for a Phoenix home?

SEER2 is the efficiency rating printed on every new central air conditioner and heat pump, and it’s one of the numbers that decides whether a system can be installed in Arizona. When you compare replacement quotes in Phoenix, SEER2 and its companion rating, EER2, tell you how much electricity each system uses to cool the house. Here is what the numbers mean and which ones matter most in desert heat.

What SEER2 measures

SEER2 stands for Seasonal Energy Efficiency Ratio 2. The U.S. Department of Energy defines it as the total heat removed from the home during the cooling season divided by the total electricity the system uses. A higher number means more cooling for each kilowatt-hour.

The “2” marks a change in how systems are tested. Starting January 1, 2023, SEER2 replaced the older SEER rating. The Department of Energy says the new test procedures were designed to better reflect real-world installation and use. The main change, as Carrier explains it, is that the test now accounts for more resistance from ductwork. Johnstone Supply gives the numbers: for typical ducted systems, test external static pressure rose from as low as 0.1 to 0.5 inches of water.

Because the test is tougher, the same equipment earns a lower number under SEER2 than it did under SEER. AHRI, the HVAC manufacturers’ trade association, lists 14.3 SEER2 as equivalent to 15 SEER. That matters when you read older articles or compare an old system’s label with a new quote: the numbers aren’t on the same scale.

The federal minimum for a new AC in Arizona

Federal efficiency standards vary by region. Arizona is in the Southwest region, along with California, Nevada, and New Mexico, and in the Southwest the standards are enforced by the date a system is installed, not the date it was made.

For systems installed since January 1, 2023, the Department of Energy sets these Southwest minimums:

• Split-system air conditioners under 45,000 BTU per hour (under about 3.75 tons): 14.3 SEER2 and 11.7 EER2. The EER2 minimum drops to 9.8 for systems rated 15.2 SEER2 or higher.
• Split-system air conditioners of 45,000 BTU per hour or more: 13.8 SEER2 and 11.2 EER2, or 9.8 EER2 at 15.2 SEER2 or higher.
• Single-package air conditioners: 13.4 SEER2 and 10.6 EER2.
• Split-system heat pumps: 14.3 SEER2 and 7.5 HSPF2 (the heating rating), the same nationwide.

The Southwest is the only region with an EER2 minimum for central air conditioners. The North and Southeast regions set SEER2 minimums only. A contractor quoting you a system in Phoenix should be quoting equipment that meets these numbers.

Why EER2 matters in Phoenix heat

SEER2 averages efficiency across a whole cooling season. EER2 measures something narrower: the Department of Energy describes it as peak-load efficiency, how efficient a system is “when it’s working its hardest.” Carrier notes that EER2 is measured at a single high outdoor temperature, 95°F.

That is an ordinary day in Phoenix. National Weather Service data for 1991 to 2020 shows the city’s first 95°F day arrives around April 12 on average and the last around October 18, with 100°F days on average from about May 2 to October 5. From spring through fall, many Phoenix afternoons are at or above the EER2 test point, so the EER2 rating is a better guide than SEER2 to how a system performs in the hours that drive your summer bills.

Carrier also notes that in hotter climates where the AC runs constantly, a higher SEER2 rating can pay back through lower energy bills. When you compare two quotes, look at both numbers, not just the SEER2 on the brochure.

What ENERGY STAR means now, and what to ask

ENERGY STAR no longer certifies air conditioners that only cool. The EPA ended its ENERGY STAR specification for central air conditioners on February 1, 2026. Heat pumps are still covered: under ENERGY STAR’s Version 6.2 specification, a split-system heat pump needs at least 15.2 SEER2, 11.0 EER2, and 7.8 HSPF2 to qualify. If a quote calls a cooling-only system “ENERGY STAR,” ask what that refers to.

If you’re weighing a heat pump, see what a heat pump replacement costs in Phoenix. For cooling-only systems, see what a new AC costs in Phoenix.

When you compare quotes, ask each contractor for:

• The SEER2 and EER2 ratings of the exact system being quoted
• Confirmation that it meets the Southwest minimums for installation in Arizona
• The capacity in BTUs per hour, so you know which minimum applies
• For heat pumps, the HSPF2 rating and whether the system meets ENERGY STAR criteria