SEER2 Explained: Efficiency Ratings for Inverter Units

SEER2 is the U.S. Department of Energy's current test standard for measuring cooling-season efficiency of air conditioners and heat pumps. It replaced SEER on January 1, 2023. Federal minimums are 13.4 SEER2 for central AC in the Northern region, 14.3 SEER2 for central AC in the Southern regions, and 14.3 SEER2 nationwide for heat pumps. Inverter units post higher SEER2 numbers because their variable-speed compressors modulate output instead of cycling on and off at full power.

The rest of this article breaks down what SEER2 actually measures, how it differs from the old SEER rating, what counts as a "good" SEER2 for an inverter unit, and how the number relates to your real electric bill. If you want the wider picture first, start with our inverter air conditioner guide, then come back here for the efficiency detail.

SEER2 is the total cooling a unit delivers over an average cooling season, in BTUs, divided by the total electricity it uses during that season, in watt-hours. It is a seasonal average, not a peak number, and it is measured under the DOE's M1 test procedure, which took effect January 1, 2023.

The M1 procedure raised the external static pressure used during testing from 0.1 to 0.5 inches of water column. That change is important. Static pressure represents the resistance the blower has to push against, everything from ductwork to the filter to the coil. The old SEER test assumed almost none of that resistance existed. The DOE's updated procedure is closer to what a real home actually looks like once the unit is installed.

The higher the SEER2, the more cooling you get per watt-hour of electricity across a normal summer. It does not tell you peak performance on the hottest day of the year. That is what EER2 is for, which we cover further down.

SEER and SEER2 use the same underlying formula. The difference is the test conditions. Because the M1 procedure uses roughly five times the static pressure of the old test, the exact same physical unit will earn a slightly lower number under SEER2 than it did under SEER. A unit that tested at 16 SEER before typically lands around 15.2 SEER2 under the new standard.

Practically, the numbers are not directly comparable across the transition. If you are cross-shopping equipment, look only at SEER2 on new units and ignore any lingering SEER-only literature. Trying to convert between the two invites errors.

Most homes have ductwork, filters, and coils that push back against airflow. The old SEER test underestimated all of that. Under the old rules, a unit could earn a strong lab number and then underperform in a real house. SEER2 closes that gap by testing under a static pressure closer to what a typical duct system actually presents to the blower.

The DOE splits the country into regions for central air conditioner minimums, then applies a single nationwide minimum for heat pumps. If a unit is manufactured for U.S. sale, it has to meet these baselines. Here is where things sit today.

These minimums are the floor. Anything sold new has to hit them. Inverter units generally sit well above the floor, which is why so many of them qualify for utility rebates and federal tax credits.

For inverter units, the interesting range starts above the federal minimum. Entry-level inverter units generally post SEER2 ratings in the 15 to 17 range. Mid-tier units land in the high teens. Premium ductless mini-splits and high-end central inverter units routinely test at 18 to 22 SEER2 or higher.

The reason inverter units post higher numbers than single-stage equipment comes down to how they operate. A single-stage compressor is either running at 100% or off. Every start pulls a surge of current, and every cycle wastes some of the energy that went into cooling the coil to the correct temperature.

An inverter compressor modulates its speed continuously, often between roughly 10% and 100% of capacity. On a mild day, it might loaf along at 30%. On a hot afternoon, it ramps up gradually. Because it rarely cycles off and never slams on at full power, it wastes less energy on start-up and holds the coil at a steady temperature that maximizes heat transfer. The SEER2 test, which averages performance across the season rather than measuring a single peak, rewards that behavior.

If you want to see how this plays out across specific product lines, our Goodman inverter AC lineup guide walks through the SEER2 ratings for each Goodman inverter model side by side. To browse current models across brands, head to our category page for inverter AC units.

SEER2 is a lab number. It is a much more honest lab number than SEER was, but it is still a controlled test. Two homeowners with the exact same unit can see very different electric bills, and the reasons usually have nothing to do with the equipment.

• Home envelope. Insulation levels, window quality, air sealing, and shading matter enormously. A well-sealed home cuts the cooling load your unit has to fight against.
• Duct condition. Leaky or uninsulated ducts can waste a significant portion of the conditioned air before it reaches a register. The SEER2 test simulates duct resistance but not duct leakage.
• Sizing. An oversized unit short-cycles even if it is an inverter. A properly sized inverter unit spends most of its life at part load, which is where its efficiency advantage lives.
• Installation quality. Correct refrigerant charge, proper airflow across the coil, and clean line-set brazing all affect real-world performance. A high SEER2 unit installed poorly can perform worse than a lower SEER2 unit installed well.
• Thermostat behavior. Frequent large setpoint swings force any unit to work harder. Inverter units are designed to hold a steady temperature, and that is where they save the most energy.
• Electricity rate. Higher rates make efficiency matter more. Lower rates lengthen the payback period on premium equipment.

Inverter units deliver comfort improvements that a SEER2 number doesn't fully capture. Longer, gentler run cycles keep the indoor coil cold for extended periods, which pulls more humidity out of the air. Drier air feels cooler at the same thermostat setting, so some households can raise their setpoint a degree or two without losing comfort. Steady, modulated operation also eliminates the temperature swings common with single-stage equipment, and the outdoor unit runs noticeably quieter because it rarely starts at full power.

SEER2 is the seasonal average for cooling. Two other numbers show up on the same rating plate.

EER2 measures cooling efficiency at a single high outdoor temperature, typically 95°F. It tells you how the unit performs at peak demand rather than across the whole season. In hot, dry climates where the unit spends long stretches near its design condition, EER2 is arguably more predictive of real bills than SEER2. The Southwest region minimum standards include an EER2 requirement for that reason.

HSPF2 is the heating-season equivalent of SEER2 for heat pumps. It divides total heating output over the season by total electricity used. The federal minimum for split-system heat pumps is 7.5 HSPF2 nationwide. For inverter heat pumps, HSPF2 in the 8 to 10 range is common, and cold-climate models often push higher. If you are shopping heat pumps for a cool or cold climate, HSPF2 matters at least as much as SEER2. Our companion piece, HSPF2 explained for cold-climate inverter heat pumps, goes deeper.

Together, SEER2, EER2, and HSPF2 give a fuller picture than any single number. SEER2 is the headline. EER2 tells you how the unit handles the hottest day. HSPF2 tells you how it handles winter.

SEER2 is the U.S. Department of Energy's cooling-season efficiency rating for central air conditioners and heat pumps. It measures total BTUs of cooling delivered over an average season divided by total watt-hours of electricity used. It replaced the older SEER rating on January 1, 2023, using a tougher test procedure that better reflects real ductwork conditions in a typical home.

For the same physical unit, SEER2 is slightly lower than SEER, typically by about 4 to 5 percent. That is because the M1 test procedure applies five times the static pressure of the old test. The unit did not get less efficient. The test simply reflects real-world duct resistance more accurately. Compare only SEER2 to SEER2 when shopping new equipment.

Per the U.S. Department of Energy, split-system central air conditioners must hit 13.4 SEER2 in the Northern region and 14.3 SEER2 in the Southeast and Southwest regions. Split-system heat pumps must hit 14.3 SEER2 nationwide, along with 7.5 HSPF2. The Southwest also carries an EER2 minimum tied to unit capacity. These are floors, not targets.

For inverter units, 16 to 18 SEER2 is a solid mainstream range, and 18 to 22 SEER2 or higher is common on premium central units and ductless mini-splits. Anything above the federal minimum will meaningfully out-perform a single-stage unit at part load, which is where inverter units spend most of their operating hours. Match the tier to your climate and cooling hours.

Higher SEER2 means the unit converts electricity into cooling more efficiently, so on paper it should lower bills. The actual savings depend on your home's insulation, duct condition, sizing, installation quality, thermostat habits, and local electric rates. A high-SEER2 inverter unit installed in a leaky house with bad ducts will not deliver its rated efficiency. Fix the envelope alongside the equipment.