SEER2 is the standard way to compare the seasonal cooling efficiency of central air conditioners and heat pumps. It's a useful tool when you're shopping for a new system — but it isn't a prediction of your power bill, and it can't tell you whether a system is sized or installed correctly. Here's how to use it.
You may still hear the older term SEER. Since 2023, equipment has been rated under the newer SEER2 test, which better reflects the airflow resistance of real ductwork. The two numbers come from different tests, so there's no exact conversion between them.
What SEER2 means
SEER2 stands for Seasonal Energy Efficiency Ratio 2. It compares how much cooling a system delivers over a representative cooling season to the electricity it uses in a standardized lab test. Higher is more efficient. Keep in mind:
It's a lab rating under a defined test.
It applies to a specific matched combination of indoor and outdoor equipment.
It's great for comparing systems side by side.
It doesn't guarantee your energy use, comfort or equipment life.
The outdoor unit's rating depends on which indoor coil or air handler it's paired with. Always ask for the AHRI reference number or certificate for the exact combination in your quote.
SEER2, EER2 and HSPF2
SEER2 measures cooling efficiency across a range of seasonal conditions. EER2 measures cooling efficiency at one hot test condition — useful context for a South Carolina summer. HSPF2 measures a heat pump's seasonal heating efficiency. If you're comparing heat pumps, look at all three.
South Carolina minimum ratings
For residential split-system central air conditioners installed in South Carolina, the regional minimum is:
14.3 SEER2 for systems below 45,000 Btu/h
13.8 SEER2 for systems at or above 45,000 Btu/h
For residential split-system heat pumps, the federal minimum is 14.3 SEER2 and 7.5 HSPF2. These are minimums, not a recommendation to buy the highest rating available.
A real-world comparison
Say you have two bids. Bid A lists only an outdoor model. Bid B lists the outdoor unit, indoor coil, furnace, AHRI reference number, 15.2 SEER2 and 12 EER2. You can't fairly compare them until Bid A gives you the exact indoor match and certificate. Then compare capacity, stages, controls, duct and electrical work, refrigerant piping, permits and warranty.
A higher SEER2 doesn't settle it, either. A well-sized system with a solid installation can outperform a higher-rated one connected to leaky or restrictive ducts.
Why your results may differ
Real homes aren't test labs. Your actual energy use depends on weather, thermostat settings, insulation and windows, air leaks, equipment sizing, duct condition, filter and blower setup, installation quality, household habits and your electric rate. That's why no one should promise a specific bill reduction from SEER2 alone.
Sizing comes first
Bigger isn't better. An oversized AC cools the house quickly and shuts off before it removes much humidity — a real problem in the Midlands. An undersized one struggles on the hottest days. A contractor should size the system based on your home's size, construction, insulation, windows, orientation and air leakage, not just the old unit's nameplate.
Ducts and installation matter
Ask your contractor to check return and supply capacity, static pressure, duct leaks and airflow to problem rooms. Fixing ductwork can deliver more comfort than moving up an equipment tier. Installation should follow the manufacturer's requirements for refrigerant piping, pressure testing, evacuation, charging, drainage, electrical and airflow setup.
Your bid checklist
Ask how the system size was determined.
Get all indoor and outdoor model numbers in writing.
Request the AHRI certificate for the exact match.
Compare SEER2 and EER2, plus HSPF2 for heat pumps.
Compare staging, controls, sound and humidity performance.
Get a clear scope for ducts, drainage, electrical, refrigerant lines and permits.
Read the parts and labor warranties.
Note: the old rule that "16 SEER equals ENERGY STAR" no longer applies. Current ENERGY STAR criteria use SEER2, EER2 and HSPF2.
Rebates and refrigerants in 2026
The federal Section 25C tax credit ended for equipment installed after December 31, 2025. If you're a Dominion Energy South Carolina residential electric customer, you may still qualify for utility rebates on ENERGY STAR central air conditioners and heat pumps installed by a licensed contractor — check the current requirements before you buy.
And if your current system uses R-410A, it's still legal to repair. See our R-410A guide for details.
The bottom line
Use SEER2 to compare exact, certified equipment combinations — alongside EER2, HSPF2, sizing, ductwork, installation and warranty. The highest number isn't automatically the best system for your home or budget. For more ways to cut cooling costs, see how to lower your energy bill.
Shopping for a new system? On Call's NATE-certified technicians install Trane single-stage, two-stage and variable-speed systems sized for your home, and we've served Columbia and the Midlands since 2011. You'll get the AHRI-matched models and one firm installed price in writing, and your technician can walk you through financing in person. Learn more about AC installation or call (803) 781-4357.
