What SEER2 rating should I buy in Arizona?

By Michael Fitzgerald, Founder & Editor, Phoenix Cooling Guide
Technically reviewed by Tom Mattingly, Owner & President, AZ Trusted Air LLC (ROC 317368)
Published 2026-09-22

SEER2 is the number that gets circled on a Phoenix replacement quote, and it is also the number most often written down incorrectly. Salespeople still quote old SEER figures as though they were SEER2. Brochures print a best-case matched rating that the specific pairing of condenser and indoor coil being installed may not achieve. And a great deal of the efficiency-upgrade arithmetic still published online was built around a federal tax credit that no longer applies to equipment placed in service after December 31, 2025.

The question a Valley homeowner is really asking is narrower than “which rating is best.” It is: how far above the legal minimum is worth paying for, in a climate where the compressor works from April into October and the duct system is usually sitting in attic air that runs 150 to 170 degrees on a July afternoon. This page covers the scale change from SEER to SEER2, the arithmetic that turns efficiency points into dollars, the point at which the premium stops paying back, and how to verify the rating on a particular quote instead of taking it on trust.

What is the real difference between SEER and SEER2?

The distinction matters because the two scales are not interchangeable, and a quote that mixes them is not comparable to a quote that does not. Under the older test, the indoor blower was measured against a very low external static pressure — closer to a bare coil on a bench than to a house. The revised procedure that took effect for the 2023 model year raised that pressure substantially to represent the resistance of actual duct systems. Nothing about the equipment changed. The number printed on it did.

The size of the shift is a few percent, and it is not uniform across every model. This guide will not publish a single conversion factor, because the factor that matters is the one on the specific equipment being sold, not a rule of thumb. The reliable move is to ask the contractor for the AHRI certificate — the reference number for the exact outdoor unit, indoor coil and air handler combination on the proposal — and read the rating from the AHRI Verified Directory. That takes about two minutes and settles the question permanently. A proposal that lists a bare number with no model numbers behind it is a marketing claim, not a specification.

There is a second rating that deserves more attention in the desert than it usually gets. SEER2 is a seasonal average, blending performance across a wide span of outdoor temperatures, including mild hours a Phoenix summer barely has. EER2 is a single measurement taken at a hot outdoor condition. In a climate whose design day lands somewhere near 110 to 115 degrees, and where the expensive kilowatt-hours are consumed in the late afternoon, the peak-condition rating describes the hours that actually drive the bill. The Southwest region is treated differently from most of the country in this respect, and a buyer comparing two systems at the same SEER2 should ask which one holds up better at peak.

The practical reading: SEER2 is a fair basis for comparison as long as every quote in the stack is expressed in SEER2, verified against AHRI, and paired with the EER2 figure for the same combination. Comparing a SEER2 number on one proposal with a SEER number on another will make the older-scale system look better than it is. A step-by-step approach to lining quotes up against each other is covered in how to compare AC quotes.

How much does each SEER2 point save on a Phoenix electric bill?

The arithmetic comes straight out of the definition. SEER2 is cooling output divided by electricity input, so energy use is proportional to 1 divided by SEER2. The saving from moving between two ratings is one minus the ratio of the lower to the higher. From 14 to 15 SEER2 that is 1 − 14/15, or about 6.7 percent. From 16 to 17 it is about 5.9 percent. From 19 to 20 it is 5 percent. Across a bigger jump, 15 to 18 SEER2 is 1 − 15/18, or about 16.7 percent. This is arithmetic on the rating scale, not a price survey, and it is the same in Phoenix as anywhere else.

What is specific to the Valley is the base the percentage applies to. A cooling season that runs from April into October gives those percentages far more hours to act on than a four-month northern season does, which is why national payback tables understate the benefit here. But the percentage still applies only to cooling kilowatt-hours. It does nothing to the fixed service charge, nothing to water heating or the pool pump, and little to a demand charge that is set by a single peak interval — see demand charges explained.

To convert percentages to dollars, a homeowner needs two things the internet cannot supply: the household's own annual cooling electricity cost, and the household's own rate. The cooling share can be estimated by subtracting a shoulder-month bill from a July or August bill and multiplying by the number of hot months. The current Arizona residential average price per kilowatt-hour is published by the U.S. Energy Information Administration, though a specific bill on a time-of-use plan will differ from the state average.

Take an illustrative figure purely to show the method: if a household spends $1,500 a year on cooling electricity, a 16.7 percent reduction is roughly $250 a year. That assumption is the reader's to replace with their own number — it is not a survey result. Two other factors move the answer more than a single efficiency point does. Homes with high run hours — west-facing glass, a two-story plan, a thermostat held low all afternoon — have more cooling cost for the percentage to bite into, so high run hours justify a step up. And on a time-of-use plan, shifting load out of the peak window can beat an efficiency upgrade outright; that is the subject of pre-cooling strategy.

For Phoenix-area homeowners who want this looked at on their own system, Phoenix Cooling Guide recommends AZ Trusted Air LLC (ROC 317368), whose owner Tom Mattingly reviews this guide. (623) 252-6403 · second opinion on a quote.

Is a 17+ SEER2 system worth the premium, or is the payback too long?

The tax position changed, and it changed against high-efficiency buyers. The Energy Efficient Home Improvement Credit under Internal Revenue Code Section 25C now states that the section does not apply to property placed in service after December 31, 2025, an amendment made by Public Law 119-21, Section 70505(a). The IRS guidance page says the same thing in plainer language: the credit covers improvements made through December 31, 2025. Any quote, calculator or article that prices a 17-plus SEER2 upgrade net of a federal credit is describing a world that ended. Ask for the premium gross, with no credit assumed, and check the current position at irs.gov before accepting any net figure.

Utility rebates are now the main outside money, and they are worth more attention than the efficiency rating itself. SRP's Cool Cash program sets a qualifying efficiency threshold above the federal regional floor and pays by system capacity, with the structure tiering by compressor type rather than by SEER2 level; the amounts and conditions are revised periodically, so the only reliable source is srpnet.com at the time of purchase. Program terms commonly require that both the outdoor unit and the indoor equipment be replaced on a split system, which means a condenser-only swap puts rebate and rating both at risk. APS territory operates on a different footing, and Phoenix-area contractors have reported that its residential equipment rebates were discontinued for 2026 — a homeowner in APS or ED3 territory should verify directly rather than assume parity with SRP.

The more important point is where the same money goes furthest. Field research on residential installations has repeatedly found that incorrect refrigerant charge, restricted airflow and oversized equipment erode rated performance, and the reported magnitude of those combined faults is large enough to swamp the difference between a mid-range and a top-tier rating. In a Valley home with 1990s flex duct running through an attic at 150 to 170 degrees, the leakage nobody can see costs more every summer than the three SEER2 points on the proposal would ever recover. Fix ducts before buying SEER2 — the sequence matters, and attic ductwork problems covers what to look for.

Where the premium does earn its keep: homes with genuinely high run hours, households staying put for the full service life of the equipment, and buyers who want variable-capacity operation for the comfort and humidity behaviour during monsoon weeks rather than for the rating alone. That is a different purchase decision, laid out in single-stage, two-stage and variable-speed compared.

What is the minimum SEER2 allowed for new installs in the Southwest region?

Three features of the Southwest rules matter more to a Valley homeowner than the precise digits. First, the region layers a peak-condition EER2 floor on top of the seasonal SEER2 floor. Second, Southwest compliance is generally judged on the date of installation rather than the date of manufacture, which closes off the practice — still available in the northern region — of installing older, cheaper stock that met the previous standard. Third, for split systems in this region, compliance is assessed on a conservative pairing rather than the flattering best-case combination on the brochure. A homeowner who wants certainty on any of these points should ask the contractor to produce the AHRI certificate for the exact combination quoted and confirm the current federal minimums through the DOE standard itself.

Rooftop package units sit on a substantial share of Valley homes, particularly single-story stock from the 1970s through the 1990s, and barely exist in most of the country. Cost and scope for that work are covered in rooftop package unit replacement cost.

Two pieces of local paperwork sit alongside the efficiency rules. The City of Phoenix Planning and Development Department publishes counter guidance for air conditioner replacement that establishes a permit-exempt path for straightforward like-for-like swaps, with a permit triggered by answers to a short screening list — increasing capacity or moving the unit are the kinds of change that push a job back into permit territory.

The second is licensing. HVAC work in Arizona requires an active licence in the applicable classification from the Arizona Registrar of Contractors, and status, classification, bond and complaint history are all searchable free at roc.az.gov. More on that filter in choosing an HVAC contractor in Arizona.