EER and SEER Calculator

Calculate EER and SEER ratings for air conditioning equipment based on cooling capacity and power input.

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How to Calculate EER and SEER Ratings

What Are EER and SEER?

EER (Energy Efficiency Ratio) measures cooling efficiency at a single rated condition: 95°F outdoor, 80°F indoor, 67°F wet-bulb. It is calculated as cooling output (BTU/hr) divided by electrical input (watts). A higher EER means a more efficient unit at peak conditions.

SEER (Seasonal Energy Efficiency Ratio) measures efficiency across a range of outdoor temperatures over a full cooling season. It is the total cooling output (BTU) divided by total electrical energy consumed (watt-hours). SEER is always higher than EER because part-load conditions are more efficient than peak.

The Formulas

EER = Cooling Capacity (BTU/hr) / Power Input (W)

SEER ≈ EER × 1.1 (industry approximation)

Annual kWh = (BTU/hr × Hours) / (SEER × 1000)

Actual SEER testing per AHRI 210/240 uses a weighted bin method; the 1.1× multiplier is a widely-used simplification.

Worked Example

Scenario: A 24,000 BTU central AC drawing 1,700W at rated conditions, running 1,000 hours per season.

EER = 24,000 / 1,700 = 14.1
SEER ≈ 14.1 × 1.1 = 15.5
Annual kWh = (24,000 × 1,000) / (15.5 × 1000) = 1,548 kWh
Annual cost = 1,548 × $0.15 = $232
Efficiency tier: 15.5 is between 15–18 → High Efficiency

Practical Tips

The federal minimum SEER for new central AC in the southern US (post-2023) is 15 SEER; in the north it is 14 SEER.
Upgrading from a 10 SEER unit to a 16 SEER unit can cut cooling costs by about 37%.
EER is a better metric than SEER for evaluating performance in consistently hot climates (like the Southwest US) where the unit operates near peak conditions most of the time.
Look for ENERGY STAR certified units — they exceed federal minimums and often qualify for utility rebates.

Code References

AHRI 210/240, DOE 10 CFR 430

Frequently Asked Questions

What is the difference between EER and SEER?

EER measures efficiency at a single outdoor temperature (95°F). SEER measures efficiency across the entire cooling season using varying temperatures. SEER is always higher than EER because AC units are more efficient at part-load conditions. Both are important: EER for peak-performance comparison, SEER for overall seasonal energy cost.

What is the federal minimum SEER for new air conditioners?

As of January 2023, the DOE increased minimum SEER requirements. In southern states ( hotter climate regions), the minimum is 15 SEER. In northern states, it is 14 SEER. These minimums apply to new split-system central air conditioners. Window units and PTACs have different standards.

How much does a higher SEER save on energy bills?

A higher SEER rating directly reduces energy consumption. For example, upgrading from 10 SEER to 16 SEER reduces cooling energy use by approximately 37.5%. On a typical $1,000/year cooling bill, that saves about $375 annually. The payback period depends on the price premium of the higher-SEER unit and your local electricity rate.

Is the SEER ≈ EER × 1.1 formula exact?

No, it is an approximation. The actual SEER per AHRI 210/240 is determined through a weighted bin-method test across multiple outdoor temperatures. The 1.1 multiplier is a widely-accepted industry rule of thumb that is accurate to within 5-10% for most residential equipment. For exact SEER values, always refer to the manufacturer's AHRI directory listing.