SEER Rating Converter

HVAC efficiency is measured using several rating systems.

SEER (Seasonal Energy Efficiency Ratio):

• BTU of cooling per watt-hour over a season
• Higher = more efficient
• US minimum: 14 SEER (as of 2023)

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:

• SEER 14 = EER 12.25 = COP 3.59
• SEER 16 = EER 14.0 = COP 4.10
• SEER 20 = EER 17.5 = COP 5.13
• SEER 25 = EER 21.9 = COP 6.41

Energy Star minimum: SEER 15+ for central AC.

SEER measures how much cooling an air conditioner delivers per unit of energy across a whole season, so a higher number means lower running costs. The 2023 switch to SEER2 changed the test conditions to be more realistic, which is why SEER2 figures run a little lower than the old SEER for the same unit. They aren’t directly comparable, so check which standard a spec is quoting.

The practical question is whether a high-SEER unit pays off. Going from 14 to 20 SEER cuts cooling energy substantially, but the efficient unit costs more upfront, and the payback depends entirely on how much you actually run it. In a hot climate with long cooling seasons, a premium SEER pays back quickly; in a mild one where the AC runs a few weeks a year, the savings may never cover the price difference. US minimum SEER also varies by region, with the hot South held to a higher floor than the North.