Air Source Heat Pumps

By Katie Anderson on September 27th, 2018

Operating in conjunction with a home’s existing heating system, air source heat pumps work by absorbing the natural heat from the outside air.

Air source heat pumps are capable of extracting heat from the air even when the temperature outside is as low as -15°C, so they will work all year round (although most efficiently in summer). Heat pumps are best at delivering heat at lower temperatures than a traditional gas or oil boiler, but over much longer periods.

There are two main types of air source heat pumps: air-to-water and air-to-air systems.

Air-to-water – these types of systems work with your wet central heating system and are particularly good for underfloor heating systems or larger radiators, due to the low heat released over long periods.

Air-to-air – these types of heat pumps produce warm air which is circulated through your home by fans.

How do air source heat pumps work?

1. The pump (similar to a large fan unit) is installed outside the home. The heat pumps absorb heat from the air into a fluid.

2. The fluid is pumped through a heat exchanger in the heat pump.

3. The system’s refrigeration system extracts low grade heat.

4. Once it passes through the heat pump compressor, it is concentrated into a higher temperature, which can be used to heat air or water for your home.

Would an air source heat pump be viable for my home?

If you’re interested in installing an air source heat pump, there’s a few points worth considering, including:

  • Given that air source heat pumps work best when producing heat at a lower temperature, your home needs to be well insulated for the heating system to be most effective.
  • Due to the lower water temperatures required, air source heat pumps perform better with underfloor heating systems compared to radiator-based systems, so you’ll need to take into consideration what type of heating system you’ll be using. You can boost the temperature of your hot water with an immersion heater in the hot water cylinder.
  • Air source heating systems can be placed on the ground or, ideally, fitted to a sunny wall. The unit will also need plenty of space around it to get a good flow of air.
  • Heat pumps are more financially viable if they are replacing an electricity or coal heating system. Replacing an A rated gas or oil boiler with an air source heat pump is unlikely to reduce your running costs.
  • It can sometimes be difficult to retrofit an air source heat pump into an existing home so they are usually recommended to install when other building work is being carried out or as part of a new build.
  • Air source heat pumps produce significantly less carbon emissions than other heating systems but they do use some electricity to run. This means it is not a carbon free system like solar.
  • The energy efficiency of the pump will drop in winter but it will continue to extract heat in temperatures as low as -15°C, so it will heat your home and hot water all year round.
  • ASHPs produce some noise as they operate it’s best to install the pump as far away from your main living or sleeping rooms as possible.
  • With professional servicing every 3-5 years and an annual check by you an air source heat pump can last for as long as 20 years, so it’s a long term investment.

Costs and savings

The installation of a typical air source heating system can range between £4,000 to £10,000 for a detached home.

The amount of money you can save by installing a heat pump system depends on a variety of factors, including fuel prices and what sort of system you are using to distribute heat. Things like temperature setting and learning how to use the system’s controls effectively will also factor in to the savings you can achieve.

Although the upfront installation cost can be high it’s important to consider the ongoing benefits and savings an air source heat pump can deliver.

Depending on the heating system you’re replacing you could see reduced heating bills.

Lower carbon emissions through burning less gas or oil. Although heat pumps use a small amount of electricity to run, they are far better for the environment than fossil fuel boilers.

Easy maintenance with professional servicing only needed every 3-5 years.

Potential to earn income from the government’s Renewable Heat Incentive (RHI) scheme.

What is the Renewable Heat Incentive (RHI)?

To encourage homeowners and businesses to adopt more renewable energy heating technologies the UK government introduced a financial incentive scheme: the RHI. The domestic RHI was first launched in 2014 and pays owners of renewable heating technology for every unit of energy the system generates.

Payments are made to the owner for 7 years after installation on a quarterly basis. The amount you’ll be paid depends on how much energy you generate, the current tariff (which is recalculated every quarter) and the type of renewable heating system you have.

Note: The RHI is available with air-to-water heat pumps, but not air-to-air.

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