SEER to EER Conversion Calculator — Efficiency Rating Comparison
Convert between SEER and EER efficiency ratings for air conditioning systems. SEER measures seasonal performance while EER measures performance at a specific peak condition (95°F outdoor, 80°F indoor, 50% RH).
SEER
EER
BTU/hr
hrs/yr
$/kWh
Formulas Used
SEER → EER (DOE/AHRI regression, SEER ≥ 11.5):
EER = SEER / (1 + 0.02 × (SEER − 11.5))
SEER → EER (linear approximation, SEER < 11.5):
EER = SEER × 0.875
EER → SEER (quadratic inverse):
0.02 × SEER² + 0.77 × SEER − EER = 0 SEER = (−0.77 + √(0.77² + 4 × 0.02 × EER)) / (2 × 0.02)
Power Draw:
Power (kW) = Capacity (BTU/hr) / (EER × 1,000)
Annual Energy & Cost:
Annual kWh = Power (kW) × Annual Hours Annual Cost ($) = Annual kWh × Rate ($/kWh)
Assumptions & References
- SEER (Seasonal Energy Efficiency Ratio) measures average cooling output over a full season divided by total electric energy input — AHRI Standard 210/240.
- EER (Energy Efficiency Ratio) measures cooling output at a single steady-state condition: 95°F outdoor dry-bulb, 80°F indoor dry-bulb, 50% relative humidity.
- The DOE regression formula EER = SEER / (1 + 0.02 × (SEER − 11.5)) is derived from AHRI statistical analysis of single-stage residential systems and is accurate to ±5% for most split systems.
- The simpler linear approximation EER ≈ SEER × 0.875 (Carrier Engineering Reference) is suitable for quick estimates.
- Two-stage and variable-speed systems may have EER values 5–10% higher than predicted by these formulas.
- Federal minimum SEER standards (as of 2023): SEER 14 in northern U.S., SEER 15 in southern U.S. (DOE 10 CFR Part 430).
- SEER2 (effective Jan 2023) uses a revised M1 blower external static pressure; SEER2 values are approximately 4–5% lower than legacy SEER for the same equipment.
- Annual cost estimates assume constant electricity rate and uniform load distribution across cooling hours.