Calculate the Energy Efficiency Ratio (EER) of your air conditioner or heat pump. Convert between EER and SEER ratings with this free calculator.
EER (Energy Efficiency Ratio) measures an air conditioner's efficiency at a specific outdoor temperature (typically 95°F). Unlike SEER, which averages efficiency over a range of temperatures, EER represents peak-condition performance — how well the unit performs on the hottest days when you need it most.
The formula is simple: divide the cooling output in BTU/hr by the electrical input in watts. Higher EER means better efficiency. Most residential AC units have EER ratings between 8 and 14. Commercial units often prioritize EER over SEER because they operate at full capacity more often.
This calculator computes EER from BTU output and wattage, and also estimates SEER from EER for comparison. EER is particularly important in hot, dry climates where AC units run at peak capacity for extended periods.
By calculating this metric accurately, energy analysts gain actionable insights that inform equipment selection, system design, and operational strategies for maximum efficiency and savings.
EER tells you how efficient your AC is at peak demand. This matters most in hot climates where the unit runs at full capacity frequently. Comparing EER ratings helps you choose equipment that performs well when you need it most. Precise quantification supports regulatory compliance and sustainability reporting, ensuring that energy data meets the standards required by auditors and industry certification bodies.
EER = Cooling Output (BTU/hr) / Power Input (Watts) Estimated SEER ≈ EER × 1.12 (approximate conversion)
Result: EER = 12.0
An AC producing 36,000 BTU/hr cooling while consuming 3,000 watts: EER = 36,000 / 3,000 = 12.0. Estimated SEER ≈ 12.0 × 1.12 = 13.4. This is a moderately efficient unit.
SEER is the better metric for comparing annual operating costs in typical weather. EER matters more for peak demand performance, commercial applications, and hot dry climates. In Phoenix, where the AC runs at near-full capacity for months, EER is arguably more relevant than SEER.
Commercial building standards often specify minimum EER rather than SEER because commercial systems operate at full capacity more often. The IECC and ASHRAE 90.1 standards include EER requirements for packaged and split AC systems above certain capacities.
Higher EER reduces peak electricity consumption, which can save money in two ways: lower total kWh usage and potentially lower demand charges on commercial electricity bills. Some residential utilities also charge higher rates during peak afternoon hours when AC usage is highest.
For central AC, EER 11–13 is good and 13+ is excellent. For window units, EER 10–12 is good. ENERGY STAR window units require EER 10.0–12.0 depending on size. Higher EER means lower electricity costs at peak cooling conditions.
EER measures efficiency at one specific condition (95°F outdoor). SEER averages efficiency across a range of conditions (65–104°F) weighted by typical weather. SEER is always higher than EER for the same unit. SEER ≈ EER × 1.12.
EER tells you how the unit performs on the hottest days when cooling demand and electricity rates are highest. A unit with high SEER but low EER may perform well in mild weather but struggle during heat waves.
Check the yellow EnergyGuide label on the unit, the specification sheet from the manufacturer, or search the AHRI directory (ahridirectory.org) by model number. Many units list both EER and SEER.
Yes, heat pumps have EER ratings for cooling mode. In heating mode, efficiency is measured by COP (Coefficient of Performance) at a specific outdoor temperature, or HSPF for seasonal heating performance.
Yes. Operating cost per hour = (BTU/hr / EER) / 1000 × electricity rate. For a 36,000 BTU unit at EER 12 and $0.14/kWh: cost = (36,000 / 12) / 1,000 × $0.14 = $0.42/hour.