SEER Rating Converter

HVAC efficiency is measured using several rating systems.

SEER (Seasonal Energy Efficiency Ratio):

• BTU of cooling per watt-hour over a whole cooling season
• Higher = more efficient

SEER2: the same idea measured on the test procedure that replaced it in January 2023. The new test runs the blower against realistic ductwork resistance rather than an easy bench setup, so the same physical unit scores lower.

• Roughly: SEER2 = SEER x 0.95 for split systems

EER (Energy Efficiency Ratio):

• BTU per watt-hour at a single test condition (95F outdoor)
• Roughly: EER = SEER x 0.875 (approximate)

COP (Coefficient of Performance):

• Ratio of cooling output to energy input (dimensionless)
• COP = EER / 3.412

Conversions:

The current US floor is written in SEER2, not SEER. Since January 2023 a new split-system central air conditioner has to make 13.4 SEER2 in the northern states and 14.3 SEER2 in the South and Southwest, which is about 14 and 15 in old SEER money. ENERGY STAR sits above that at 15.2 SEER2. The regional split is real: the same model can be legal to install in Ohio and illegal in Texas.

Because the floor and the labels moved at the same time, a 14 on one spec sheet and a 14 on another can be a year apart in vintage and a real step apart in efficiency. Check which standard a figure is quoting before comparing two quotes.

The practical question is whether a high-SEER unit pays off, and that is what the three optional boxes above answer. Going from 14 to 20 cuts cooling energy by 30%, but the efficient unit costs more up front and the payback depends entirely on how many hours a year it runs. In a Gulf Coast summer a premium unit pays back quickly. In a mild northern one where the AC runs a few weeks a year, the savings may never cover the price difference at all, and the money is better spent on insulation.