Seasonal Energy Efficiency Ratio (SEER) is the standard metric for rating the cooling efficiency of air conditioners and heat pumps in the United States. It represents total cooling output in BTU divided by total electrical energy consumed in watt-hours over a full cooling season, tested across outdoor temperatures ranging from 65°F to 104°F. A higher SEER number means the system uses less electricity to deliver the same amount of cooling.
SEER was defined by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) under standard AHRI 210/240 and enforced by the U.S. Department of Energy as the basis for federal minimum efficiency requirements from 1992 through 2022.
How SEER Translates to Energy Cost
The rating directly affects monthly electricity bills. A 24,000 BTU/h (2-ton) air conditioner running 1,000 hours per cooling season consumes different amounts of power depending on its SEER:
SEER |
Seasonal Energy Use |
Approx. Cost at $0.16/kWh |
10 |
2,400 kWh |
$384 |
14 |
1,714 kWh |
$274 |
18 |
1,333 kWh |
$213 |
22 |
1,091 kWh |
$175 |
Upgrading from SEER 10 to SEER 18 cuts cooling electricity use by 44%. The exact savings depend on local electricity rates, climate, runtime hours, and maintenance. Those variables also determine how much electricity an air conditioner uses per month in practice, which is often higher than the label math suggests.
SEER Ranges
Equipment manufactured before 2023 falls within a wide spectrum. Units from the early 1990s often rated between 8 and 10 SEER. Federal minimums rose to 13 SEER for northern states and 14 SEER for southern states by 2015. High-efficiency models reached 20+ SEER, with top-tier variable-speed systems pushing above 25.
How SEER Relates to Other Efficiency Metrics
SEER averages performance across the full season. EER (Energy Efficiency Ratio) tests at one fixed condition: 95°F outdoors, 80°F indoors, 50% humidity. COP (Coefficient of Performance) expresses the same relationship as a dimensionless ratio rather than in BTU per watt-hour. HSPF (Heating Seasonal Performance Factor) applies the seasonal approach to heating mode instead of cooling. Each metric captures a different slice of performance, and comparing air conditioner efficiency ratings side by side makes it easier to evaluate units across manufacturers.
Transition to SEER2
On January 1, 2023, the Department of Energy replaced SEER with SEER2 for all newly manufactured equipment. The new standard uses a harder test procedure with five times more external static pressure, producing ratings roughly 4.7% lower than SEER for the same hardware. To convert an old SEER rating to its approximate SEER2 equivalent, divide by 1.05.