COP Calculator
Efficiency Results
What Is the Coefficient of Performance (COP)?
The Coefficient of Performance is a simple ratio:
COP = Useful output ÷ Energy input
- Output is heating or cooling produced
- Input is the electrical power consumed
- COP has no units
If a system has a COP of 3, it means:
- You get 3 units of heating or cooling
- For every 1 unit of electricity used
Unlike fuel-based heaters, heat pumps move heat instead of creating it. That is why COP values can be greater than 1.
Why COP Is Important
COP gives you a real picture of efficiency. It helps you:
- Compare different HVAC systems
- Estimate running costs
- Check if a system is performing as expected
- Understand energy labels and efficiency claims
In short, COP tells you how hard your system is working for the electricity it uses.
Two Ways to Calculate COP
The calculator you shared supports two calculation modes. Each one serves a different purpose.
1. Actual Performance COP (Real-World Efficiency)
This mode calculates COP using measured system data.
Formula
Useful output power ÷ Electrical input power
What You Enter
- Output capacity
- Units supported: BTU/hr, kW, tons, watts
- Power input
- Units supported: watts, kilowatts, horsepower
The calculator converts everything into watts behind the scenes, then calculates the ratio.
When to Use This Mode
- Testing an installed system
- Comparing real equipment performance
- Evaluating energy usage at home or on-site
This is the most practical COP for everyday decisions.
2. Carnot COP (Theoretical Maximum)
This mode calculates the ideal COP, based on thermodynamics.
It assumes:
- No friction
- No losses
- Perfect heat transfer
This is not realistic, but it sets an upper limit.
What You Enter
- Hot reservoir temperature (Th)
- Cold reservoir temperature (Tc)
- Temperature unit: °C, °F, or K
- Cycle type: heating or cooling
The calculator converts temperatures to Kelvin, because thermodynamic formulas require absolute temperature.
Formulas Used
- Heating (heat pump):
Th ÷ (Th − Tc) - Cooling (AC or refrigerator):
Tc ÷ (Th − Tc)
When to Use This Mode
- Education and learning
- Engineering analysis
- Comparing real systems to theoretical limits
Real systems usually reach 30–50% of Carnot COP.
Understanding the COP Results
Once you click Calculate COP, the tool shows three results.
1. COP Value
This is the main efficiency number.
General guidance:
- COP < 1: Very inefficient
- COP 1 to 2.5: Basic efficiency
- COP 2.5 to 4: High efficiency
- COP > 4: Advanced or geothermal systems
2. Energy Efficiency Ratio (EER)
The calculator also converts COP into EER.
EER = COP × 3.412
EER is commonly used in air conditioning ratings, especially in North America. This conversion helps you compare COP-based systems with EER-rated equipment.
3. Efficiency Status
The calculator labels performance clearly, such as:
- Inefficient
- Standard efficiency
- High efficiency
- Industrial or geothermal class
The color coding makes it easy to spot how well the system performs at a glance.
Why COP Changes in Real Life
COP is not a fixed number. It changes based on:
- Outdoor temperature
- Indoor temperature
- System load
- Compressor condition
- Installation quality
Cold weather lowers COP for air-source heat pumps. Smaller temperature differences improve efficiency.
This is why real COP values are always lower than Carnot COP.
Common COP Mistakes to Avoid
- Mixing units without conversion
- Forgetting that temperatures must be absolute for Carnot COP
- Assuming COP stays constant all year
- Comparing COP values from different test conditions
The calculator prevents many of these errors by handling conversions automatically.
Who Should Use a COP Calculator?
This tool is useful for:
- Homeowners comparing heating systems
- HVAC technicians checking system health
- Energy auditors
- Engineering students
- Anyone curious about efficiency
You do not need advanced physics knowledge to get useful answers from it.