Heat Pump Coefficient Of Performance VS Seasonal Performance Factor: Understanding Heat Pump Efficiency

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  • Heat pump coefficient of performance (CoP) is a measure of your heat pump’s efficiency based on energy output vs energy consumption. The higher the CoP, the better, as this means you get more energy out of your heat pump than what you put in. A CoP of 4 means your heat pump produces 4x more energy (heat) than it consumes (electricity).
  • Heat pump seasonal performance factor (SPF) is another way to measure heat pump efficiency on average whilst factoring in seasonal performance. Heat pumps will need to work harder when air and ground temperatures are colder in winter, so will consume more energy to produce the same heat output level compared to when temperatures are warmer in summer. The seasonal performance factor accounts for this.
  • Heat Pumps UK can help you find installers of heat pumps who offer models with some of the most impressive CoP and SPF scores. Enter your postcode to see the best deals from various heat pump installers in your area for free, with absolutely no-obligation.

Your heat pump’s efficiency can be measured in two main ways: coefficient of performance (CoP) and seasonal performance factor (SPF). Both are excellent ways to simply tell how efficient a heat pump model is, but it can be confusing if you’re unsure what both stand for. It can also be confusing to see two different figures for both measures.

Below we’ll talk about how air source heat pumps and ground source heat pumps can be measured in terms of energy efficiency, explain what CoP and SPF scores are, and explore the differences between the two.

What is CoP?

CoP, or coefficient of performance, is just one way in which heat pumps are measured in terms of energy efficiency. It takes into account energy consumption vs energy production, so you get a full picture of just how efficient your heat pumps are. CoP is provided for both air source heat pumps and ground source heat pumps.

Essentially, CoP looks at the heating system in the moment, and considers how much energy you’ve had to put into the heat pump to make it work, and then looks at the energy output to see how much you get out of the heat pump compared to what you’ve put in.

CoP is expressed as a single figure, and it essentially tells you how much more energy you get out of your heat pump compared to what you’ve put in – where electrical energy is what you’ve put in, and heat energy is what you get out. For example:

  • If electricity consumption to power your heat pump is 1kW, then this is your electrical input.
  • If your heat pump produces 3kW of heat energy, then this is your heat output.
  • Your CoP will be expressed as 3, because 3 times more heat has been put out than the electrical energy put in.

How can a heat pump produce more energy than is put in?

Even if you aren’t familiar with the laws of thermodynamics, it stands to reason that if 1kW of energy is put in, 1kW of energy should be put out. The first law of thermodynamics says that energy can’t be created or destroyed, so how is it possible for a heat pump to produce more energy than is put in? Well, that’s the genius of heat pump technology.

Heat pumps do not create new energy. Instead, they use the electric energy put into the heating system AND heat already present in the air or ground. An air source heat pump draws heat from the outside air, and a ground source heat pump draws heat from the ground.

In the example above, where 1kW of energy is provided by electrical energy, and 3kW of heat output is recorded, 2kW of heat energy must be drawn from another heat source (in these cases, the air temperature or ground temperature).

The input temperature from the ground or air is then heated further using the 1kW of electrical energy, changing the output temperature and providing effective water or space heating for your home.

What factors affect the CoP of a heat pump?

One of the main factors affecting your heat pump CoP is the temperature outside. During any heating season temperatures will fluctuate, meaning your heat pump will need to work more or less, depending on the air conditioning or space heating temperatures required vs the outside temperature.

For example, if your heat pump was trying to warm your home to 17 degrees celsius, but the outside temperature was 0, then it would have to work a lot harder than if the outside temperature was 12 degrees celsius to get the output temperature desired.

The same applies to air conditioning. If it’s 25 degrees celsius outside, but you want to cool your home to 15 degrees, then again, your heat pump will require more electrical energy to reach the desired temperature compared if it was only 20 degrees out.

A good illustration of how CoPs can change throughout the year can actually be seen with a solar thermal system, which is notoriously inefficient in colder climates, but can reach a CoP of over 70 when it’s sunny out.

The seasons affect heat pumps in a similar way, although less extreme.

Will CoP scores change throughout the year?

Yes, they absolutely will. It’s quite complicated because it involves considering the primary energy factor (a measure of end user electricity consumed vs primary energy consumption), the temperature of the ground or air, and the amount of electrical energy required to power the heat pump (including where this energy is sourced from).

Since things can start to get complicated here, heat pump manufacturers provide a much simpler way for you to understand how the CoP changes throughout the heating season, by providing another figure: the seasonal performance factor (SPF).

What is SPF?

SPF, or seasonal performance factor, is another way of measuring heat efficiency for heat pumps, but it factors in how a heat pump performs during different seasons, and then provides an average score, so you know, on average, how efficient your heat pumps are throughout the year.

Essentially it will consider the total electrical energy consumed throughout the year vs the total heat output to understand the coefficient of performance on average throughout the heating season.

If the SPF is shown as 3, then it means, on average throughout the year, your heat pump will produce 3 times more heat energy than electrical energy put in. However, at certain times of the year this could be as low as 0.5 or lower, or as high as 6 or more.

Is one measure of heat pump efficiency more relevant?

The main difference between the two factors can be summarised below:

  • CoPs: Provide a snapshot of your heat pump’s efficiency performance. When heat pump manufacturers display this, they should explain where the CoP is from. It could be the maximum CoP expected, the minimum, or something else – but it will need to be clear.
  • SPFs: Provide an overview of your heat pump’s efficiency performance. This will essentially display the average CoP across the year, so whilst the CoP will sometimes be more or less than the SPF figure provided, on average it will perform at the SPF figure throughout the year.

Both are useful measures to consider.

What is a good CoP for heat pumps?

Typically, a CoP score of between 3 and 5 is considered good.

What is a good SPF for heat pumps?

An SPF score of 3.5 or above is considered good.

Heat Pump Coefficient Of Performance vs Seasonal Performance Factor: Summary

Understanding both the heat pump coefficient of performance (CoP) and seasonal performance factor (SPF) is key to understanding just how efficient heat pumps available on the market are. If you’re researching heat pump models yourself, then knowing these two figures and what they mean will be key.

However, if you don’t have the time to research different models yourself, then you should rely on heat pump installers who are more familiar with the different efficiency measures to help you make the right choice.Work with Heat Pumps UK to find installers in your area offering the best deals on the most efficient heat pumps.

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Ollie Creevy
Ollie has been writing content online about home improvements for over 3 years. With a real interest and in-depth knowledge of heat pumps and ECO home improvement measures you can use to save on your energy bills. Ollie also keeps up to date with all the Government grants available for you to take advantage of like ECO4 and the Boiler Upgrade Scheme.