Scientists are constantly looking for more eco-friendly ways to heat our homes. Boilers are getting more energy efficient all the time – but they’re not always the best way to run a central heating system. Air source heat pumps are a game changer.

What is an air source heat pump?

 A device, powered by electricity, that absorbs warmth from the air outside (even when it’s freezing cold) to heat your home. It can also be used to provide hot water.

The kit looks a bit like an air conditioning unit – quite big and not especially attractive, so you’ll probably want it installed around the side or back of your home.

Are there different types of heat pump?

• Air-to-water systems heat water which is then circulated around the home via radiators or an underfloor heating system. They can also be used to heat water in a storage tank.
• Air-to-air systems typically use fans to circulate warm air around the home and can’t be used to heat water.

Air-to-water systems are the most common.

How does it work? 

Like a fridge except that it is situated out in your garden and it works in reverse. Put simply, it takes outside air in, extracts energy from it, and blows colder air out.  This energy is absorbed by a refrigerant fluid and is used to heat water which is then pumped into your house.

It can do this even in temperatures as low as -15C, so it need not be sunny outside. A fridge uses the same technology in reverse to extract heat from its inside, which is why the space behind the appliance feels warm.

What are the benefits?

• Lower fuel bills, especially if you replace electric heating or oil.
• Potential income – through the UK government’s Renewable Heat Initiative (RHI). This is a financial incentive, where over seven years you’ll receive quarterly payments for extra green energy that you’re producing. For air source heat pumps, you’ll receive 10.18p/kWh of renewable heat and in some instances can far outweigh the costs.
• Eco-friendly -  it uses air, a renewable, natural source of energy to heat your home. While electricity is still needed, you can achieve the same amount of heating with a fraction of the energy input.
• Reduce your carbon footprint – air source heat pumps generate less CO2 than most traditional boilers.
• The pump sits outside your home – so could free up space in your kitchen or utility room
• Easy to install – all you need is enough external wall space for the unit, which makes it ideal for urban homes and small gardens. Easier to install than ground source heat pumps which need lots of ground space and expensive digging.
• There is no need for fuel deliveries or storage. No need to worry about suddenly finding that your oil tank is empty.
• Some heat pumps can also be used as air conditioning units in the summer.
• Low maintenance – some installers recommend a yearly check-up while others suggest 3-5 years.
• Typically, an air pump comes under Permitted Developments, so doesn’t need council consent (more about the exceptions below)

And what are the disadvantages?

• Electricity is still needed to power the pump, so there will still be some CO2 emissions if it’s run off the main electric supply. It’s only completely carbon-free if your heat pump is hooked to a solar power installation or wind turbine.
• Lower heat supply - the pump works most effectively at lower temperatures, so it is better suited to underfloor heating than radiator-based systems.
• A heat pump can take some time to heat your home up, so you need to plan ahead.
• As they provide a lower heat than conventional systems, your home needs to be well-insulated and draught proof to stay warm and get the energy savings.
• You will need enough space outside for the external condenser unit (about the size of an air-conditioning unit), so possibly not suited to flats.
• Loud – condenser units can be noisy and blow out cold air into the immediate environment
• Air pumps may not result in savings for homes using mains gas.
• The unit may need planning permission if installed in a listed building or in a conservation area, so check the rules with your local planning authority.

How much does it cost?

Heat pumps aren’t cheap. Typically, a domestic system costs £6,000-£8,000, according to the Energy Savings Trust. Prices vary considerably. The best way to find out how much it will cost for your home is to get quotes from several different companies.

Government grants are available through the Renewable Heat Initiative for England, Scotland and Wales to partially or fully recoup the cost. Bear in mind that in order to qualify for this grant, it must be an air-to-water heat pump and grants cannot be applied for retrospectively for existing systems.

How much will it save me?

The payback period (or time taken to recoup cost of installation) will depend on how efficiently your system runs, the system it’s replacing and RHI payments. But the savings on heating bills combined with the cash payments, means it can give an excellent return on investment which is usually repaid in 4-5 years, says Government.

It is most cost-effective if you’re air source heat pumps replaces electricity, oil or coal. If you have a gas boiler it won’t save much, according to the Energy Savings Trust and it could take many years to see a return on your investment.

Potential savings of installing a standard air source heat pump in an average sized four-bedroom detached home range from £1,315 for old electric storage heaters and £1,100 for older oil boilers to £305 for typical non-condensing gas boiler, according to the Energy Savings Trust. Figures are based on fuel prices in February 2019. Carbon savings, meanwhile, are biggest for traditional coal and oil boilers.

Ask your installer how to use the system most effectively. You’ll probably need to keep the heating on for longer but at a lower level than a conventional oil or gas boiler. 

Hybrid heat pump

In older properties, it may not be possible to insulate to a high enough standard to rely solely on an air source heat pump. In these cases, you can have another heating system, such as an oil-fired boiler or traditional gas boiler, to work alongside the heat pump. The system can be set up so both systems run at the same time or the heat pump switched off, so the boiler provides all the heat.

And finally…

While there is a long list of advantages to heat pumps, there are potential downsides too. Heat pumps aren’t suitable for every home. A tech survey by a qualified assessor is essential before installation. To reap the rewards, you need a well-insulated home, especially loft insulation.

If you are looking for help with any electrical issues, you may find some of these services useful: