Example Data Table
| Case | Capacity | Power | EER | COP | Comment |
|---|---|---|---|---|---|
| Small room unit | 12,000 BTU/h | 1,200 W | 10.00 | 2.93 | Moderate steady performance |
| Large split unit | 24,000 BTU/h | 1,800 W | 13.33 | 3.91 | Strong steady performance |
| Office unit | 36,000 BTU/h | 4,200 W | 8.57 | 2.51 | Review load and maintenance |
Formula Used
Cooling kW = BTU/h ÷ 3412.142.
Tons = BTU/h ÷ 12000.
EER = Cooling capacity in BTU/h ÷ Power input in watts.
COP = Cooling output in kW ÷ Electrical input in kW.
Estimated SEER = EER × Seasonal factor.
Annual kWh = Power kW × Hours per day × Cooling days × Duty cycle.
Annual cost = Annual kWh × Electricity rate.
Delivered cooling = Cooling kW × Sensible heat ratio × Remaining duct efficiency.
Carnot COP = Indoor temperature in kelvin ÷ Temperature difference in kelvin.
How To Use This Calculator
Enter the rated cooling capacity first. Select BTU/h, tons, or cooling kW. Add the measured or rated electrical power input. Choose watts or kilowatts. Enter indoor and outdoor temperatures for a theoretical comparison. Add your daily hours, yearly cooling days, and duty cycle. Enter the electricity rate for cost estimates. Adjust seasonal factor, duct loss, and sensible heat ratio when better data is available. Press the calculate button. The result will appear above the form and below the header.
AC Efficiency Guide
Understanding AC Efficiency
Air conditioning efficiency shows how much cooling you receive for each unit of electricity. A better score means more comfort with less wasted energy. This calculator compares capacity, electrical input, temperature lift, operating time, and seasonal use. It turns those values into EER, COP, estimated SEER, annual energy use, and operating cost.
Why Efficiency Matters
Cooling systems often run for many hours during warm months. Small efficiency differences can become large cost changes over a season. EER helps compare steady running performance. COP uses metric energy units and is useful for engineering checks. SEER estimates seasonal performance and helps compare equipment ratings. The calculator also estimates savings from a higher target rating.
What The Results Mean
A high EER or COP usually indicates efficient cooling. A lower kilowatt per ton value is usually better. Annual kilowatt hours show expected electricity use under your operating pattern. Cost depends on your local rate, duty cycle, and number of cooling days. The Carnot comparison is a theoretical benchmark. Real units never reach it, but the percentage helps reveal practical performance gaps.
Inputs That Improve Accuracy
Capacity should match the rated cooling output, not the room size. Use measured electrical input when possible. Nameplate values are useful, but real readings are better. Enter realistic daily hours and cooling days. Duty cycle should reflect how often the compressor actually runs. Seasonal factor adjusts steady performance toward expected seasonal behavior. Duct loss and sensible heat ratio show useful delivered cooling.
Using The Calculator For Decisions
Use the tool before replacing a unit, comparing models, or checking a bill. Try your current unit first. Then enter a target SEER value for a possible upgrade. Review annual savings and payback support with your own equipment price. Test different electricity rates if tariffs change. Test different duty cycles for mild and extreme weather. These comparisons make comfort planning clearer. They also help spot oversizing, poor airflow, duct leakage, or maintenance problems.
Best Use Tips
Run several cases before making a choice. Keep one case for normal weather. Keep another for peak heat. Compare the outputs side by side. If measured power is unavailable, use a conservative estimate and note the uncertainty clearly. for later review today.
FAQs
What does EER mean?
EER means energy efficiency ratio. It compares cooling output in BTU/h with electrical input in watts. Higher values usually mean better steady operating efficiency.
What does COP mean?
COP means coefficient of performance. It compares cooling output in kilowatts with electrical input in kilowatts. It is common in engineering and energy analysis.
Is SEER the same as EER?
No. EER describes steady performance at a fixed condition. SEER estimates seasonal performance over changing conditions. This calculator uses a seasonal factor to estimate SEER.
What is a good EER value?
A higher EER is better. Many older systems may fall near 8 to 10. Efficient units often exceed 12, depending on size, design, and test conditions.
Why include duty cycle?
Most systems do not run continuously. Duty cycle estimates the active compressor time. It makes annual energy and cost results more realistic.
What is duct loss?
Duct loss is cooling lost through leakage, heat gain, or poor insulation. Higher duct loss reduces delivered cooling and lowers practical performance.
Can this estimate my bill?
Yes. Enter your power use, operating hours, cooling days, duty cycle, and electricity rate. The result gives estimated annual energy cost.
Why use Carnot COP?
Carnot COP is a theoretical limit. Real air conditioners perform below it. The comparison helps show how far practical equipment is from ideal performance.