What Is a SEER Rating?
When shopping for an air conditioner, you'll quickly encounter the term SEER — Seasonal Energy Efficiency Ratio. It's the most important number for understanding how much electricity an AC unit consumes relative to the cooling it delivers.
Specifically, SEER measures the total cooling output (in BTUs) over a typical cooling season divided by the total electrical energy input (in watt-hours) during the same period. The higher the SEER number, the more cooling you get per unit of electricity — meaning lower monthly bills.
SEER vs. SEER2: What Changed?
Starting in January 2023, the US Department of Energy updated its testing methodology to better reflect real-world installation conditions. The new standard is called SEER2. Ratings under the new standard are slightly lower numerically than the old SEER ratings for equivalent units — so a unit that was rated SEER 16 might be rated SEER2 15.2.
When comparing units, make sure you're comparing the same rating system (SEER vs. SEER2) to avoid confusion.
Minimum SEER Requirements by Region
The US government mandates minimum efficiency standards that vary by climate region:
| Region | Minimum SEER2 (Split Systems, as of 2023) |
|---|---|
| North (cooler climates) | 13.4 SEER2 |
| South & Southwest (hotter climates) | 14.3 SEER2 |
These are minimums — for better savings, look for units well above these thresholds.
How Much Does a Higher SEER Rating Actually Save?
The savings from a higher SEER unit depend on your local electricity rates, climate, and how much you run your AC. As a rough illustration:
- Upgrading from a SEER 10 system (older) to a SEER 20 system can cut cooling energy consumption by roughly 50%.
- Going from SEER 14 to SEER 18 yields a meaningful but more modest improvement — around 22% less energy used for cooling.
In regions with hot summers and high electricity rates, a high-SEER unit can pay for the premium cost difference within just a few years.
Is the Highest SEER Always the Best Choice?
Not necessarily. There are some important trade-offs to consider:
- Upfront cost: High-SEER units (20+) carry a significant price premium. In mild climates with short summers, the payback period may be very long.
- Complexity: Very high-efficiency units often use variable-speed compressors and more sophisticated electronics — they can cost more to repair.
- Sweet spot: For most homeowners in warm climates, a unit in the 16–18 SEER2 range offers an excellent balance of upfront cost and long-term savings.
Other Efficiency Ratings to Know
- EER / EER2: Energy Efficiency Ratio — measures efficiency at a single peak temperature (95°F). More relevant for consistently hot climates.
- HSPF / HSPF2: Heating Seasonal Performance Factor — applies to heat pumps and measures heating efficiency.
- ENERGY STAR: A certification indicating a unit exceeds minimum efficiency standards by a meaningful margin. Always a reliable shortcut when comparing options.
Practical Tips for Maximizing Efficiency Regardless of SEER
- Keep the air filter clean — a dirty filter can slash effective efficiency dramatically.
- Use a programmable or smart thermostat to avoid cooling an empty house.
- Seal duct leaks — leaky ductwork can waste 20–30% of conditioned air.
- Add insulation and weatherstripping to reduce heat gain in the home.
- Use ceiling fans to allow the thermostat to be set a few degrees higher.
Understanding SEER ratings empowers you to make an informed purchase decision — and to accurately estimate the long-term operating cost of any unit you're considering.