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What are COP and SCOP and why are they so important?

July 11, 2023

scop vs cop diagram

Heat pumps are not new technology but the increase in popularity for home installations coupled with the recent energy price hikes has seen a lot of concern about the real world running costs.

Fortunately we have an accurate way to find out the overall efficiency for heat pumps - COP and SCOP

What is the Coefficient of Performance (COP)?

In its simplest terms, the Coefficient of Performance (COP) is a measure of the efficiency of a heating (or cooling) system at that moment in time. It is the ratio of useful heat movement per work input, or in other words, the ratio of the energy output of the heat pump to the electrical input it requires to run.

A heat pump's COP typically ranges between 2.0 and 5.0 for air source heat pumps, and can be even higher for ground source heat pumps. What this means is that for every one unit of energy the heat pump uses (like electricity, for instance), it can produce between 2 to 5 units of heat or cooling, depending on the specific model and environmental conditions.

It's important to note that COP varies with outside temperature for air source heat pumps. When it's very cold outside, the COP can be lower because the heat pump has to work harder to extract heat from the outside air.

What is the Seasonal Coefficient of Performance (SCOP)?

While the COP provides a snapshot of a heat pump's efficiency at a given moment, the Seasonal Coefficient of Performance (SCOP) offers a broader view of the heat pump's efficiency over an entire heating season. This is also sometimes called SPF or Seasonal Performance Factor.

The SCOP is the ratio of the total amount of heat delivered divided by the total amount of energy consumed over the same period. This measure takes into account the variations in temperature over the season and provides a more realistic and comprehensive measure of a heat pump’s annual energy efficiency. It is most accurate once it has gone through a whole year as the Winter will be lower, in the Summer the air is hotter so even though the heat pump has to run higher to heat the hot water it has more energy to do that with.

SCOP values typically range from 3.0 to 4.0 for modern air source heat pumps. Like COP, the SCOP can be influenced by several factors such as the type of heat pump, the quality of the installation, and the specific climate conditions of the location.

The minimum that MCS allow for compliant heat pump installations is 2.8, the average is 3.4.  VitoEnergy project aim to be above 4 and at the time of writing have an average of 4.1.

Why are COP and SCOP important?

COP and SCOP are critical factors to consider when selecting a heat pump. A higher COP or SCOP means the system is more efficient, potentially leading to significant energy savings over the system's lifetime. By choosing a heat pump with a high COP or SCOP, you can reduce your carbon footprint and energy bills. 

For a regular 3 bedroom house the difference between 2 and 4 could easily be over £2,000 a year!

However, while COP and SCOP are important, they should not be the sole determinants when selecting a heat pump. Other factors, such as the heat pump's capacity, its compatibility with your existing system, and its initial cost, should also be taken into account. 

What can influence COP and SCOP?

Correct and diligent design is crucial here, understanding the relationship between the heat loss of the building, the pipe sizing, insulation, emitter sizing and more will enable a low temperature system design.

If you would like to learn how to maximise efficiency with SCOP, read our ultimate heat pump guide.

Conclusion

Understanding COP and SCOP can help you make an informed decision when it comes to selecting the best heat pump for your needs. They provide a measure of a system's performance, enabling you to balance your environmental responsibilities with the practical considerations of heating and cooling your space.

Ask your installer (including us) what SCOP is being aimed for, this should be in a heat loss and part of a performance estimate before installing. You can then ask them how they will measure and evidence that, we collect our performance data and will be publishing it so you don’t have to just take our word.

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