SEER To COP Converter
Convert SEER, SEER2 or EER to an approximate COP, and convert COP back to a Btu per Wh efficiency number for air conditioners and heat pumps.
Quick SEER Values
These buttons load common comparison values. Keep the final buying decision tied to the actual product rating, climate, installation and use pattern.
Efficiency Conversion Result
4.69 COP
A SEER value of 16 converts to an approximate COP of 4.69 before any seasonal caution adjustment.
16.00 Btu/Wh
4.69
0.75 kW
GBP 0.21
1 COP = 3.412 Btu/Wh
COP 4.69 to 16.00
Seasonal comparison
Quick Conversions
| SEER Or EER | Approx COP | Meaning In Plain Terms | Important Limit |
|---|---|---|---|
| 13 | 3.81 | About 3.8 units of heat moved per unit of electricity. | Seasonal rating, not one fixed outdoor condition. |
| 16 | 4.69 | Common comparison point for efficient cooling equipment. | Installation quality can change real use. |
| 18 | 5.28 | Higher seasonal rating than SEER 16. | Do not compare directly with heating COP at a single temperature. |
| 20 | 5.86 | Strong seasonal cooling rating in Btu per Wh terms. | Part-load behaviour matters. |
| 25 | 7.33 | Very high converted number, often tied to variable-speed equipment. | Check the actual certified rating. |
Conversion Formula And Method
COP = SEER / 3.412141633.
COP = SEER2 / 3.412141633.
COP = EER / 3.412141633.
EER-style value = COP x 3.412141633.
Adjusted COP = COP x (1 – caution adjustment percentage).
Estimated input power = output kW / adjusted COP.
Cost per running hour = input power kW x electricity price per kWh.
The factor comes from the relationship between Btu per hour and watts. One watt is about 3.412 Btu per hour, so a Btu per Wh efficiency number can be converted to a dimensionless COP by dividing by 3.412. The problem is not the arithmetic; it is the meaning of the rating. SEER and SEER2 are seasonal cooling measures, while COP is often quoted at a stated test condition.
SEER, SEER2, EER And COP Are Not Identical Labels
SEER is a seasonal cooling efficiency ratio. SEER2 is a newer seasonal test metric used in the United States with updated test conditions. EER is an efficiency ratio at a specified condition. COP is a power ratio and is widely used for heat pumps, chillers and refrigeration. These labels are related because they compare useful thermal output with electrical input, but they do not always describe the same test.
That is why this page says “approximate COP”. A product with SEER 18 does not necessarily have COP 5.28 at every outdoor temperature. Real output can change with compressor speed, coil condition, refrigerant charge, duct losses, fan power, defrost, thermostat pattern and outdoor air temperature. Use the converter for comparison, then read the product datasheet for rated capacity and condition-specific COP.
Worked Efficiency Examples
SEER 16 Air Conditioner
SEER 16 divided by 3.412 gives COP 4.69. If the cooling output is 3.5 kW, the simple input power example is about 0.75 kW before any caution adjustment. At 28p per kWh, that is about 21p per running hour.
COP 4 Heat Pump
COP 4 multiplied by 3.412 gives an EER-style value of about 13.65. That helps compare a COP quote with a Btu per Wh style rating, but the operating condition still needs to match.
Cautious Planning
If a seasonal rating looks optimistic for an older installation, entering a 15% caution adjustment reduces the converted COP before the running-cost example. This is a planning stress test, not a certified rating.
When To Use This Converter
Use this converter when a specification sheet, forum post, installer quote or overseas product label gives SEER, SEER2, EER or COP and you need a common comparison scale. It is helpful for first-pass comparison between air conditioners, air-source heat pumps, mini-splits and cooling equipment described in different markets.
Do not use it as the only basis for buying or sizing equipment. A heating system in a UK home needs room heat loss, flow temperature, radiator or underfloor capacity, hot water demand, outdoor design temperature, noise, installer competence and tariff context. Cooling equipment needs room load, solar gain, duct or pipe run, fan power and humidity control. The converter is one part of a larger specification check.
Datasheet Checks Before Comparing Products
Before treating two converted COP values as a product ranking, check the rating standard, test temperature, output capacity and whether fan or pump power is included. A high SEER value can come from strong part-load performance, while a heating COP may be quoted at a mild outdoor temperature that does not match a cold UK design day. If one product lists seasonal cooling efficiency and another lists heating COP at a stated flow temperature, the arithmetic conversion is useful for vocabulary, but it is not a like-for-like tender comparison.
Also compare the capacity beside the efficiency number. A unit can have a high ratio at a low output but still be the wrong size for the room or home. For quotes, ask the installer to state design heat loss, flow temperature, emitter capacity, weather compensation setting, sound level, refrigerant pipe length and whether any backup heater is assumed. If electricity cost is the main concern, run the converter with a cautious adjustment and then compare that result with annual kWh estimates from the actual design.
FAQ
What is the formula for SEER to COP?
Divide SEER by 3.412141633. For example, SEER 16 is about COP 4.69.
Is SEER2 converted the same way?
The arithmetic factor is the same, but SEER2 comes from a newer test basis. Treat the result as an approximate comparison, not a direct product guarantee.
Is COP the same as efficiency percentage?
No. COP is a ratio. COP 4 means useful thermal output is 4 times the electrical input under the stated conditions.
Can a COP be above 1?
Yes. Heat pumps move heat rather than creating all heat directly from electricity, so COP above 1 is normal.
Can I use this for heating COP?
You can compare units, but heating COP depends strongly on outdoor temperature and flow temperature. Use datasheet values for heating performance.
Why is the running-cost result only an example?
It uses output divided by converted COP. Actual running cost depends on load, cycling, weather, controls, fan power and tariff.
Sources
- National Institute of Standards and Technology. (2008). Guide for the Use of the International System of Units (SI). NIST Special Publication 811. https://www.nist.gov/pml/special-publication-811
- U.S. Department of Energy. (2023). Central air conditioners and heat pumps test procedure. Energy.gov. https://www.energy.gov/eere/buildings/appliance-and-equipment-standards-program
- ENERGY STAR. (n.d.). Heating and cooling equipment. ENERGY STAR. https://www.energystar.gov/products/heating_cooling
- Chartered Institution of Building Services Engineers. (n.d.). Heat pumps. CIBSE. https://www.cibse.org/knowledge-research/knowledge-portal