Quick EER Calculator
Use this tool to calculate the Energy Efficiency Ratio (EER) for an air conditioner or cooling system.
What is an Energy Efficiency Ratio (EER)?
The Energy Efficiency Ratio (EER) is a performance metric used to evaluate how efficiently a cooling appliance converts electrical energy into cooling output at a specific operating condition. In practical terms, EER tells you how many BTUs of cooling you get for each watt of electricity consumed.
A higher EER value means better efficiency. If two units provide the same cooling capacity, the one with the higher EER generally uses less electricity under similar conditions.
How to use this energy efficiency ratio calculator
Step-by-step instructions
- Enter the cooling capacity value from your equipment specification sheet.
- Select the cooling capacity unit (BTU/hr, tons, or cooling kW).
- Enter the electrical power input and choose watts or kilowatts.
- Click Calculate EER.
- Optionally add electricity rate and runtime hours to estimate operating cost.
Typical input examples
- Small room AC: 8,000 to 12,000 BTU/hr, around 700 to 1,200 W.
- Central split system: 2 to 5 tons, power often in kW.
- Commercial cooling unit: capacities often listed in tons or cooling kW.
EER formula and conversion notes
The direct equation is simple:
Useful conversions used by this calculator:
- 1 ton of refrigeration = 12,000 BTU/hr
- 1 kW (cooling) = 3,412.142 BTU/hr
- COP (Coefficient of Performance) ≈ EER ÷ 3.412
What is a good EER rating?
"Good" depends on equipment type, climate, and testing conditions, but as a rough guide:
- EER below 8: lower efficiency by modern standards.
- EER 8 to 10: acceptable for older or budget systems.
- EER 10 to 12: solid efficiency for many current units.
- EER above 12: high efficiency, especially in hotter conditions.
For hot climates where peak temperature performance matters, EER can be more informative than seasonal metrics.
EER vs SEER vs COP
EER
Measured at a specific outdoor/indoor test condition. Good for comparing peak-condition efficiency.
SEER (Seasonal Energy Efficiency Ratio)
Reflects expected efficiency over an entire cooling season with varying temperatures.
COP (Coefficient of Performance)
A dimensionless metric widely used in engineering. COP can be converted from EER using: COP = EER / 3.412.
How to improve your effective cooling efficiency
- Keep air filters clean and replace on schedule.
- Seal duct leaks to reduce cooled-air losses.
- Use smart thermostats and reasonable set points.
- Shade outdoor condenser units when possible, while maintaining airflow clearance.
- Perform annual HVAC maintenance checks before peak summer demand.
- Improve insulation and air sealing to reduce cooling load.
Frequently asked questions
Can EER be used for heat pumps?
Yes, during cooling mode. For heating performance, other ratings such as HSPF or COP in heating mode are commonly used.
Does a higher EER always mean lower electric bills?
Usually yes for comparable usage, but actual cost also depends on runtime, electricity prices, thermostat settings, climate, home insulation, and system sizing.
Why did my calculated EER look unusually high or low?
Check units first. A mismatch between tons, BTU/hr, watts, and kilowatts is the most common source of errors.
Final thoughts
If you're evaluating AC units, comparing existing equipment, or estimating operating costs, EER is a practical and reliable metric. Use the calculator above to get a fast estimate, then combine that with installation quality and maintenance practices for best real-world performance.