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Heat pumps will play a crucial role in meeting Scotland’s net zero targets, and we’re here to help people make the change. Replacing your boiler with a new heat pump could help lower your energy bills and reduce your home’s carbon emissions.
Heat pumps—air source, ground source, or water source—are a way of heating your home and providing hot water. These modern, low-carbon heating systems are much more energy efficient than boilers and electric heating. Heat pumps could help lower your energy bills and reduce your home’s carbon emissions.
Heat pumps efficiently move heat from the surrounding air or ground into your home, requiring much less energy than traditional heating systems like burning gas or oil. Heat pumps use electricity to operate, but as our grid shifts to cleaner energy sources like renewables, heat pumps become increasingly low carbon over time.
There are three types of heat pump: air source, ground source, and water source. Read on to find out how they work, the benefits, potential costs and savings, and what to think about before installing.
The air source heat pump is the UK's most common heat pump. Its popularity is thanks to its relatively easy installation, lower associated costs and financial support and benefits.
Air source heat pumps need electricity to run. They extract renewable heat from the environment, transforming the air’s heat energy into heating and hot water. The heat output is greater than the electricity input, which makes it an energy-efficient heating system.
Heat pumps have two main components and work in a way similar to fridges. In simple terms, they move heat from one area to another. Air source heat pumps use a refrigerant - a fluid that evaporates at a very low temperature - to draw heat energy from outside air. The evaporated refrigerant is compressed, giving off a lot of heat energy.
There are two types of air source heat pump: air-to-water and air-to-air.
Traditional central heating systems use a boiler to warm water and radiators, often using high temperatures. With an air-to-water heat pump system, heat energy warms water for your hot water cylinder and radiators.
Air-to-water heat pumps are more energy efficient at lower temperatures, requiring good radiator design controlled to release heat over longer periods, which can make a big difference to its running costs.
With an air-to-air heat pump, heat energy warms air that is then circulated around your home. An air-to-air heat pump does not provide hot water.
It's worth considering a few things to fully understand the implications of installing an air source heat pump.
The higher your heat demand, the larger the heat pump you'll need.
Insulation and draught proofing can reduce your heat demand, as well as improve the comfort of your home. You can get financial help to insulate your home.
Home Energy Scotland Grant and LoanA heat pump needs plenty of space to allow for good airflow and is usually fitted on the ground or an outside wall. Check with your local authority if you require planning permission.
Inside, you’ll need room for controls, a compressor (which is usually smaller than a standard gas boiler), and a hot water cylinder. Underfloor heating and larger radiators work best. Installers can advise you on what would be best for your own situation.
Heat pumps are typically relatively quiet. They will emit a noise similar to that of an air conditioning unit.
Heat pumps work most efficiently delivering low-temperature water. Therefore, a heat pump system should run for extended periods with larger radiators or underfloor heating to reach your desired thermostat temperature. This is different to a gas, oil, or LPG-fuelled boiler, as these systems deliver higher-temperature water. It’s more efficient for these systems to be switched on for less time.
Many systems will be classed as a ‘permitted development', which means they can be installed without the need for planning permission. However, we recommend you check with your local authority if you are unsure.
Heating water can limit the system's overall efficiency. Solar water heating or an electric immersion heater can help with the hot water supply. It’s best to talk to your installer about your needs because every home will have different hot water usage requirements.
Air source heat pumps require very little maintenance. You should check the air inlet grill and evaporator are debris-free at least once a year. Remove any plants growing near the heat pump. Your installer may suggest checking your home's central heating pressure gauge from time to time. You can ask them to list all the maintenance requirements. We'd also recommend a professional heat pump service every two to three years.
You could consider a ground source heat pump if you have ample garden space outside.
Ground source heat pumps, also known as geothermal heat pumps, extract heat from the ground via a loop of pipes buried underground. Inside these pipes, called a ground loop, the ground source heat pump circulates an antifreeze and water solution. The fluid absorbs heat from the ground.
The fluid passes through a compressor in the heat pump, increasing the fluid’s temperature. The fluid’s heat then transfers to radiators and underfloor heating systems. It can provide hot water in your home, too.
The cooled solution returns to the underground pipes to reheat in a continual cycle, providing heating and hot water for the heat pump's lifetime.
As underground temperatures are pretty constant (between 10-13°C), ground source heat pumps are more consistently efficient than air source heat pumps.
The ground loop length required depends on how much heat you need. Longer loops draw more heat but need more space. People with smaller gardens may be able to drill a vertical borehole 90-160m deep for their ground loop.
There is plenty to consider before installing a ground source heat pump.
Your garden doesn't need to be big, but it must be accessible to digging machinery and be suitable for a trench or a borehole. The space required varies (horizontal pipes need more room), and the ground must be appropriate for digging. Vertical boreholes are typically more expensive than horizontal trenches as you’ll need a geological survey and more specialised equipment.
Insulation and draught proofing can reduce your heat demand and improve the comfort of your home. Financial help is available to insulate your home.
See what funding is availableGround source heat pumps can perform better with underfloor heating or systems that use larger radiators.
It may take several weeks to install an entire system. Once installed, the pipes are not visible, and you can use your garden as usual.
Ground source heat pumps are generally very quiet. You may hear some compressor noises at the indoor unit, such as a low hum or buzz, similar to the noise of a refrigerator.
You'll need space for a hot water cylinder. They can usually go into a cupboard or sometimes where the boiler used to be. The size you'll need will depend on how much water you use; for example, a large family will need more hot water and a larger cylinder than someone living on their own. Discuss your hot water needs with your installer.
Ground source heat pumps work most efficiently delivering low-temperature water. Therefore, a heat pump system should be run for extended periods with larger radiators or underfloor heating to reach your desired thermostat temperature.
Always check with your local authority if you need planning permission, although it is not a likely requirement.
Ground source heat pumps are low maintenance. Annual checks may include inspecting the heat pump’s external pipes, fittings, and electronics. Have a professional service of the heat pump every four to five years.
Water source heat pumps work very similar to ground source heat pumps, except the pipes are submerged in water—a river, loch, large pond, or borehole—rather than underground.
The water body’s heat transfers into a fluid in the pipes, then passes through a compressor in the water heat pump. The compressor increases the fluid's temperature so that you can use it for hot water and central heating.
Water transfers heat better than air, and water temperatures are generally stable all year-round (7-12°C).
You need a large watercourse nearby, like a large lake or a river, and one that won't freeze. The higher the heat demand, the more extensive the body of water you'll need for the pipes.
Underfloor heating and large radiators work best with water source heat pumps, and your home needs space for the heat pump. Insulation and draught proofing can reduce your heat demand and improve the comfort of your home.
Open loop systems will require water extraction and discharge permission (called abstraction) from the Scottish Environment Protection Agency (SEPA). Abstraction is separate from planning permission. Open and closed loop systems don't require planning permission, but check with your planning authority in case.
A water source heat pump could deliver all your home’s heating and hot water needs. It's best to consult an expert; there are many things to consider in determining whether your water body is suitable for a water source heat pump.
Heat pumps are most cost-effective when replacing electric or gas heating systems. They may not reduce your energy bill when replacing a newer gas boiler, but they do emit fewer carbon emissions.
Air source heat pumps use electricity, so you will still have energy bills. However, compared to the older, less efficient heating systems they replace, their energy efficiency should further reduce energy bills.
A typical air source heat pump can cost around £14,000. The cost will depend on the heat pump size and the work required in the home, such as pipework, hot water cylinders and upgraded radiators. Most systems come with a two to three-year warranty, and a well-maintained system can last up to 20 years.
In Scotland, the Home Energy Scotland Grant and Loan can help with installation costs.
These are the potential annual savings of installing a standard air source heat pump in an average-sized, three-bedroom detached home in Scotland, England, and Wales.
Ground source heat pumps use electricity, so you will still have energy bills - but they are energy efficient. Replacing an old oil or LPG boiler could save over £800 a year. Most ground source heat pumps come with a two to three-year warranty, and a well-maintained system can last up to 20 years.
They do represent a significant investment. A typical system costs around £28,000, rising to around £49,000 if you need to install a borehole. Running costs will depend on several factors, including your heat demand, electricity tariff, and how long the system is left running.
In Scotland, the Home Energy Scotland Grant and Loan is available to help with installation costs.
These are the potential annual savings of installing a standard ground source heat pump in an average-sized, four-bedroom detached home in Scotland, England, and Wales.
Our heat pump heroes are homeowners who’ve already made the switch to save energy and cut carbon emissions and are keen to encourage others to do the same. Read their stories to learn more about their experiences and what it's really like installing and living with this low-carbon technology.
Be inspired by the heat pump heroes
