Although there are different kinds of heat pumps, they all work in the same way. Heat pumps transfer heat from the outside environment into a building through a four-step process:
This is known as a refrigeration cycle. This heat pump diagram illustrates the process:
Heat pumps take in heat from the air or ground or sometimes water, transferring it to a heat exchanger that contains a liquid refrigerant. This refrigerant absorbs heat from the outside and evaporates, turning it into a low-pressure, low-temperature gas.
The gas is transferred to an electrically powered compressor that compresses the refrigerant. This compression increases the pressure of the gas, which raises the gas temperature.
The hot gas reaches the heat exchanger, where it’s circulated and transfers its heat to a cold water circuit. This causes the water to heat up as it absorbs heat from the gas. Once the water has reached the desired temperature, usually around 55 degrees, it’s sent to your home’s radiators and underfloor heating to warm your house.
By transferring heat to the water circuit, the refrigerant cools down enough to turn it back into a liquid.
The cooled refrigerant moves through an expansion valve, which lowers the pressure and allows it to absorb more heat energy. From there it’s pumped back into the heat exchanger to repeat the cycle.
There are some differences in how heat pumps work, depending on what type of heat pump you have:
Heat pumps are suitable for all kinds of homes. It’s a common heat pump myth that certain kinds of houses can’t have heat pumps installed.
The kind of heat pump that suits your home usually comes down to:
Use our online assessment tool, Go Renewable, to find out what renewable technologies, including heat pumps, are suitable for your home.
Air source heat pumps are the most common type of domestic heat pump in the UK and are suitable for most types of home. They’re relatively small and cheaper to install than other types of heat pump. The heat pump is normally provided as a ‘monoblock’ that sits outside the home. The heat pump unit is around the size of two wheelie bins side by side.
Ground source heat pumps are better suited to those who have a large garden or outdoor space to run a loop of underground pipes or sink boreholes. They tend to be more efficient than air source heat pumps but are considerably more expensive to install.
For all heat pumps you need space to put a hot water cylinder, ideally inside the house. Having underfloor heating usually works well for heat pumps. You may need to upgrade any radiators to have a higher surface area, which are suitable for heat pumps.
For more information, read our guide to the differences between air source and ground source heat pumps.
If you live in a smaller property, like a flat or park home, you may be better suited to an air-to-air heat pump. These heat pumps heat your home using fans rather than radiators or underfloor heating.
Heat pumps are more efficient than other heating systems and generally produce around three times more energy than they take in – 300% efficient. They’re more efficient as the heat they provide is harvested from the environment rather than coming directly from an energy source, such as natural gas.
Compare this to an A-rated gas boiler, which has an efficiency of around 85%. This means that for every unit of gas used in the boiler, it produces 0.85 units of heat. And oil boilers are 88% efficient, so produce 0.88 units of heat for every unit of oil burnt.
In a heat pump the amount of heat produced for every unit of electricity used is known as the Coefficient of Performance (CoP). So, if a heat pump has a CoP of 3.0, then it gives out three units of heat for every unit of electricity it uses.
Every heat pump has a published datasheet telling you what its measured CoP is. This published CoP is measured at a single point in time, under specific test conditions.
However, in real life, heat pumps experience external temperature variations throughout the year that affect their efficiency. So the CoP isn’t always helpful in understanding what your heat pump will cost to run over the year.
To help with this, the seasonal coefficient of performance or seasonal performance factor (SPF) shows the efficiency of the heat pump averaged across the whole year.
Heat pump installers must calculate the SPF based on their system design for your home. This calculation shows how the heat pump should perform given:
Your heat pump installer should share this calculation with you before they start any work. The SPF gives you a better indication of your expected system efficiency, running costs and possible running cost savings than the CoP figure.
The cost to install a heat pump largely depends on what kind of heat pump you’re looking at:
The cost of a heat pump installation is also influenced by:
There are different funding options available to help to cover your installation costs, depending on where you live.
On average, heat pumps cost around £1,540 to run per year.
Your specific running costs will depend on a range of factors including:
This largely depends on what heating system you’re replacing.
Generally, the high efficiency of heat pumps means that it should be cheaper to run than most other fuel types.
If you have a gas boiler (or often an oil boiler in Northern Ireland), heat pumps are likely to be slightly more expensive to run.
But, as energy prices fluctuate over time, we expect that heat pumps will become the cheapest as well as the lowest carbon form of heating available.
Here are the typical savings you can expect to see from the two most common types of heat pump:
In general, no – you shouldn’t need planning permission to install a heat pump. This is because most heat pump installations are considered to be a ‘permitted development’ provided you meet certain conditions such as the heat pump not being within one metre of a neighbour’s boundary.
But there are exceptions. For example, if you live in a listed building or a conservation area. It’s best to check with your local planning department before committing to installing a heat pump.
Find out more about permission for installing renewables.
You should also tell your local district network operator (DNO) that you’re planning to install a heat pump. The DNO is the company responsible for bringing electricity from the network to your home.
Your heat pump installer will have all the information you need to complete the relevant forms and will often do this for you.
To find out more about registering a heat pump in England, Scotland and Wales, check out the UK Government website.
Research from acoustic experts and interviews with residents with heat pumps reveal that they’re about as loud as a fridge or a gas boiler. In fact, those with heat pumps installed said they were more likely to notice the sound of traffic outside their home than their heat pump.
Heat pump noise is typically in the range of 40 to 60 decibels. You may find they are a little louder in colder temperatures as they work harder. But you can still have a normal conversation right next to them. Additionally, some manufacturers offer ultra quiet models.
Last updated: 21 October 2024