Introduction to heat pumps


As the UK adapts to meet our net zero ambitions and tackle the climate emergency, one solution for our homes is to switch from fossil fuels to renewable energy. Heat pumps are increasingly popular but they are still less well understood than other types of heating.

In this guide, we aim to give you an overview of the technology. This could be useful if you are considering making this change or move into a home with a heat pump already installed.

This is part one of a three-part guide to heat pumps. Check out the other guides in the series.

Part two – Using your heating controls (heat pumps)

Part three – Heat Pump Myth Buster

 

What is a heat pump?

You may be forgiven for believing heat pumps are a revolutionary new technology. Actually, they have been in our homes for decades. You probably already have one and don’t even realise it. Did you know your fridge freezer is a heat pump? The ones we install to heat our homes work the same way, only in reverse!

Heat pumps work by absorbing warmth from one of three sources: the air, the ground or water. They use this warmth or thermal energy to heat your home and hot water. Air-source heat pumps are the most common and they are likely to be the type you will have installed in your home.

 

How do heat pumps work?

Heat pumps require electricity to work. This is used to capture the thermal energy from the source (air, ground or water) and move it into our homes.

Importantly, heat pumps run far more efficiently than gas boilers, or even other electric heating systems. Most boilers run at around 80-90% efficiency, whereas a well-installed air-source heat pump could run at around 300% efficiency. Simply put, this means one unit of electricity can produce around three units of heat.

If you want to understand the science behind the technology, we recommend reading the Energy Saving Trust’s in-depth guide to heat pumps.

 

What is the difference between types of heat pumps?

 

Air source heat pump

We can take a reasonable guess that this is the type you’re most likely to encounter. The other two types require specific conditions that mean they’re not suitable for many homes. Air source are also the cheapest and easiest to install in your home.

Air source heat pumps use an external fan unit to absorb thermal energy from the air outside your property. This is used to heat water in a central heating system. The hot water is fed into radiators or underfloor heating.

 

Ground source

A common misconception is that ground source heat pumps use geothermal energy (heat from the Earth’s crust). Actually, ground source heat pumps absorb the energy from the sun that is stored in shallow ground around your home.

If you have a ground source heat pump installed you will probably need to have trenches dug across some ground, around one metre below the surface. Ground source heat pumps can also be installed using vertical boreholes. However, this is a much more expensive and difficult process.

An installer will lay pipes along the trenches. Refrigerant carried by the pipes captures the heat and an indoor unit transfers it to the heating system.

Due to the way that ground source heat pumps are installed, they are usually only viable for rural properties with plenty of land.

 

Water source

Water source heat pumps extract thermal energy from a nearby water source such as a loch or large pond. They may also work if you have nearby rivers.

Water source heat pumps are usually only viable under very specific conditions and require a specific amount of space and a suitable nearby body of water.

As such, they are very rare and not suitable for the vast majority of homes.

 

Home insulation

Installing a heat pump is not dependent on having a super-insulated home. However, a more insulated home will help the heat pump run more efficiently as there will be less heat loss from the property. If you are looking at installing a heat pump, we always recommend a ‘fabric first’ approach, where you upgrade insulation before changing your heating system.

 

Funding

You may be able to get support to meet the cost of a new installation from Home Energy Scotland’s Grant and Loan scheme.

 

More advice

Would you like more advice on heat pumps or to see if a heat pump is right for your home? Cosy Kingdom is a free and impartial energy advice service available to everyone living within Fife.

Our energy advisors can be contacted by: