Equipment · 7 Min Read

What Is SEER2? Efficiency Ratings Explained for Homeowners

SEER2, EER2 and HSPF2 explained in plain language, what the current minimums are in California, and how much efficiency is worth paying for.

By the Superior Air team · CSLB #669421 · Updated September 8, 2026

Key points

SEER2 measures how much cooling an air conditioner or heat pump delivers per unit of electricity over a season. Higher is better. EER2 measures the same thing at a single hot-day condition, and HSPF2 is the heating equivalent for heat pumps.
SEER2 replaced SEER in 2023 with a tougher test, so a SEER2 number reads about 4.5 percent lower than the SEER number for the same unit. Compare like with like.
Current federal minimums for the Southwest region are 14.3 SEER2 for most split air conditioners and 14.3 SEER2 with 7.5 HSPF2 for heat pumps. Confirm at the time of purchase. ENERGY STAR thresholds are higher.
In San Diego the value of extra efficiency depends on your zip code. Inland Climate Zone 10 homes run the AC far more hours than coastal Climate Zone 7 homes and pay back a higher tier faster.

The short answer

SEER2 stands for Seasonal Energy Efficiency Ratio 2. It is the total cooling an air conditioner or heat pump delivers over a typical cooling season, in BTUs, divided by the electricity it uses to do it, in watt-hours. A 16 SEER2 unit produces 16 BTUs of cooling for every watt-hour of electricity, averaged across a season's mix of mild and hot days. Higher is more efficient. The "2" means the rating was measured under the test procedure that took effect on January 1, 2023, which is stricter than the one it replaced, so SEER2 numbers are not interchangeable with the SEER numbers on older equipment.

For a homeowner, the rating answers one question: how much electricity will this system use for the cooling my house needs? It does not tell you whether the system is sized correctly, whether the ducts leak, or whether the installer charged it properly, and those three things affect your bill at least as much.

SEER2, EER2 and HSPF2: what each one measures

Three ratings appear on new equipment, and a fourth on furnaces. They answer different questions.

The efficiency ratings on residential HVAC equipment and what each one tells you.
Factor	What it measures	When it matters	Applies to
SEER2	Cooling delivered per watt-hour, averaged over a season of varying outdoor temperatures	Your total summer electric bill	Air conditioners and heat pumps
EER2	Cooling delivered per watt-hour at one steady condition: 95°F outdoors, full load	Peak demand on the hottest afternoons; the number that matters most inland	Air conditioners and heat pumps
HSPF2	Heat delivered per watt-hour over a heating season	Your winter electric bill with a heat pump	Heat pumps only
AFUE	Share of the gas burned that becomes heat in the house over a year	Your winter gas bill with a furnace	Gas furnaces

A few things to notice. SEER2 rewards equipment that runs efficiently at part load on mild days, which is where variable-speed compressors shine. EER2 is measured flat out on a hot day, so two units with the same SEER2 can have different EER2 ratings, and the one with the higher EER2 will cost less to run through an Escondido heat wave. HSPF2 applies only to heat pumps and is the number to look at if the system will heat your home; our heat pump comparison covers what it means in a San Diego winter.

Why SEER became SEER2

The Department of Energy changed the test procedure in 2023. The old SEER test ran the indoor blower against very little resistance, an external static pressure of about 0.1 inches of water column, which is nothing like a real duct system. The new procedure, called M1, raises the external static pressure to 0.5 inches for ducted equipment, closer to what a blower sees in a real attic duct run. Working harder against that pressure uses more electricity, so the same physical unit scores lower on the new test.

The rule of thumb is that SEER2 reads about 4.5 percent lower than SEER for the same unit: a 16 SEER system re-rated under M1 comes out around 15.2 SEER2. The conversion is approximate and varies by equipment, but it is close enough to compare an old rating with a new one. EER2 and HSPF2 shifted in the same direction for the same reason.

This matters when you compare your existing system with a replacement. A condenser installed in 2008 with a 13 SEER sticker is roughly 12.4 SEER2 on paper, and after 18 summers of coil fouling and refrigerant drift it performs well below that. The gap between old and new is wider than the two stickers suggest.

Current minimums and what ENERGY STAR adds

Federal minimums vary by region because a Phoenix summer is not a Portland summer. California sits in the Southwest region, which has the highest requirements in the country and is the only region with an EER2 floor as well as a SEER2 floor.

Minimum efficiency for new split-system residential equipment sold in California. Confirm current figures at the time of purchase.
Factor	Federal minimum, Southwest region	ENERGY STAR
Split-system AC, under 45,000 BTU	14.3 SEER2, plus an EER2 minimum	Higher; check the current ENERGY STAR specification
Split-system AC, 45,000 BTU and up	13.8 SEER2, plus an EER2 minimum	Higher; check the current ENERGY STAR specification
Split-system heat pump	14.3 SEER2 and 7.5 HSPF2	Higher SEER2 and HSPF2 thresholds; check the current specification

These are the current federal minimums as we understand them. Confirm the figures at the time of purchase, because the standards and the ENERGY STAR specifications are revised periodically. Two consequences follow. First, any new system sold in California already meets a standard that would have counted as high-efficiency equipment fifteen years ago. Second, a "high efficiency" label on a proposal means nothing on its own. Ask for the certified SEER2, EER2 and HSPF2 figures for the exact matched combination of outdoor unit and indoor coil, which the manufacturer publishes through AHRI.

One related change: new equipment from 2025 uses A2L refrigerants, R-454B or R-32, in place of R-410A. That is a refrigerant change rather than an efficiency change, but it means a new condenser cannot be paired with an old coil, so the efficiency you buy is the rating of the matched pair.

How much efficiency is worth paying for in San Diego

The arithmetic is simple. The electricity a system uses for a given amount of cooling is inversely proportional to its rating, so the saving from one SEER2 to another is roughly one minus the old rating divided by the new one. Replacing a unit performing at 10 SEER2 with one rated 15.2 SEER2 cuts cooling electricity by about a third. Moving from 15.2 to 18 SEER2 saves a further 15 percent or so of what is left, on a system that already uses much less.

What decides whether that is worth paying for is how many hours the system runs, and in San Diego County that varies more than almost anywhere in the country.

Coastal, Climate Zone 7. Point Loma, Pacific Beach, La Jolla, Encinitas, Carlsbad, Oceanside. The marine layer does most of the cooling. Many homes run the AC for a few hundred hours a year, concentrated in September and October. Going from the federal minimum to a top-tier system saves a modest amount per year, and the payback on the extra cost is long. A quality installation at minimum or mid-tier efficiency is usually the best value.
Inland, Climate Zone 10. Escondido, Poway, San Marcos, Santee, El Cajon, La Mesa, Ramona. Summer afternoons are routinely in the 90s and heat waves push past 100. The system can run a thousand hours or more per year. Here a higher tier pays back faster, EER2 matters because so much of the runtime is at peak conditions, and a variable-speed system's ability to idle at low speed through a warm evening is worth having.
In between. Mira Mesa, Scripps Ranch, Rancho Bernardo, Carmel Valley, Chula Vista. The canyons and mesas sit on the boundary. A mid-tier system, roughly 16 to 17 SEER2, is the common answer.

There is a second reason to consider higher tiers that has nothing to do with the bill. Variable-speed equipment runs quieter, holds temperature more evenly, and removes more moisture on the humid September days coastal homes get. For some homeowners that comfort is the reason, and the savings are a bonus.

The rating is a ceiling, not a guarantee

The SEER2 number is measured in a laboratory with a matched coil, a correct refrigerant charge, correct airflow and no duct losses. In a house, every one of those can fall short.

Refrigerant charge. A system 10 percent undercharged loses a meaningful share of its capacity and efficiency. California's energy code requires third-party refrigerant charge verification on most changeouts for exactly this reason.
Airflow. A new variable-speed condenser attached to an old single-speed blower, or to ducts too small for the airflow it needs, cannot deliver its rated efficiency. The blower is part of the rating.
Duct leakage. Attic ducts in 1970s tract homes across Mira Mesa, Clairemont and El Cajon commonly leak 20 to 30 percent of the air the system moves into the attic. A 16 SEER2 unit feeding those ducts performs like a much lower one. Our ductwork page explains how leakage is measured and fixed.
Sizing. An oversized system short-cycles and never reaches the steady operation the rating assumes. The sizing guide covers why this is so common.

The point is that installation quality is worth at least as much as the next efficiency tier. A 15.2 SEER2 system installed correctly on tight ducts will outperform an 18 SEER2 system installed on leaky ones.

Reading the numbers on a proposal

A proposal that takes efficiency seriously lists the model numbers of the outdoor unit and the indoor coil or air handler, the AHRI reference number for that combination, and the certified SEER2, EER2 and, for heat pumps, HSPF2. If the proposal shows only a single number or a range, ask for the certificate. If two proposals quote different efficiencies, check whether one is quoting SEER and the other SEER2, because the older number flatters the equipment. Our contractor guide has a fuller checklist.

Maintenance matters too. A clean coil and a correct charge keep a system near its rating, which is what an annual maintenance visit checks and records.

How Superior Air approaches this

We treat efficiency as one line in the decision, not the headline.

Start with the load and the ducts. The load calculation sets the capacity, and the duct test tells us whether the ducts can deliver the airflow the equipment needs. The efficiency tier comes after those two.
Match the tier to the climate zone. For a coastal home we usually present a minimum-compliant option and a mid-tier option and explain the small difference in expected use. For an inland home the mid-tier and high-tier options get more weight, and we look at EER2 as well as SEER2.
Quote certified ratings. Every option on our written proposal lists the matched combination and its AHRI-certified SEER2, EER2 and HSPF2 figures. We do not quote SEER on new equipment.
Install to the rating. Refrigerant charged by weight, airflow measured, static pressure recorded, and the third-party verification passed before the job closes.

To see options for your home, schedule a consultation. For what drives the total cost beyond efficiency, the AC replacement cost guide is the next read, and the AC replacement page covers the service itself.

Is SEER2 the same as SEER?

No. SEER2 is measured under the M1 test procedure that took effect in January 2023, which runs the indoor blower against a higher external static pressure than the old SEER test. The same unit scores about 4.5 percent lower on SEER2 than on SEER. When you compare an old sticker with a new proposal, convert one to the other or you will overstate the old system.

What SEER2 rating should I get in San Diego?

It depends on where the house is. On the coast in Climate Zone 7, where the marine layer keeps cooling hours low, a well-installed system at or a little above the federal minimum is usually the best value. Inland in Climate Zone 10, where the system may run a thousand hours or more a year, a mid-tier or high-tier system pays back faster and EER2 matters as much as SEER2. We show the trade-off in the proposal rather than picking a number in advance.

Will a 20 SEER2 system cut my electric bill in half?

Only the cooling portion of the bill, and only if the old system was performing at about 10 SEER2 and the new one is installed to its rating. Lighting, appliances, the water heater and everything else on the bill do not change. For a coastal home that runs the AC a few weeks a year, the total bill may barely move; for an inland home the cooling share is large enough that the savings are noticeable.

What is a good HSPF2 rating for a heat pump in San Diego?

The current federal minimum for split heat pumps in the Southwest region is 7.5 HSPF2; confirm the figure at the time of purchase. Because San Diego winters are mild and heating hours are short, the difference between a minimum and a high HSPF2 rating shows up less on the bill here than in a cold climate. Sizing and thermostat setup, which determine whether backup heat strips ever run, affect the winter bill more than the rating does.

Heat pump vs. AC and furnace in San Diego →

Does a higher SEER2 rating mean a better air conditioner?

It means a more efficient one in the laboratory. Whether it performs better in your house depends on the sizing, the refrigerant charge, the airflow and the ducts. A minimum-efficiency system installed correctly on tight ducts will outperform a top-tier system installed on leaky ones, which is why we treat installation quality and duct condition as part of the efficiency decision.