Air Source Heat Pumps

Welcome to a series of four short video clips designed to show what you can do in your home to produce electricity and/or hot water for your use.

The information and views provided are based on actual use by Chew Magna residents who have installed these technologies and have been using them for years.  This means you are getting actual operational experience and not just marketing views from the equipment supplier!

Some of the issues raised will be specific to the location and not associated directly with the technology and these will be highlighted.

  • An ASHP, also referred to as an air-to-water source heat pump, transfers heat from the outside air to water that heats your rooms via radiators or underfloor heating.  It can also heat water stored in a hot water cylinder for your hot taps, showers and baths.  Heat from the air is absorbed into a fluid that then passes through a heat exchanger into the heat pump, which raises the temperature and transfers that heat to water.
  • ASHP are the most common type in the UK.  As with a gas fired boiler using a wet heating system they use a piping system to move the hot water around the house to the underfloor heating, or large wall-mounted radiators.  The unit needs to be located outside the house, where it is fitted to a wall or placed on the ground and must have space around it to allow a good flow of air.  The following photo shows a typical ASHP installation attached to the outside of a house.
  • The most common type of ASHP is an air-to-water heat pump that comes in two types: monobloc and split systems.  A monobloc system has all the components in a single outdoor unit, with pipes carrying water to the central heating system and a hot water cylinder inside your home, while a split system separates the components between indoor and outdoor units.
  • The figure below shows the basic principle of how an ASHP works.
  • Monobloc systems tend to be cheaper and quicker to install and don’t take up as much space but are slightly less efficient than split systems.  The efficiency gain from split systems comes from some of the heat transfer taking place inside the building where it is warmer, resulting in less heat being lost.  If you’re not limited by space inside your home, consider the extra cost of a split system.  The choice of system will depend on your budget and available space.
  • The government is providing grants to encourage property owners to install low carbon heating systems such as heat pumps, through the Boiler Upgrade Scheme (BUS), to help property owners overcome the upfront cost of low carbon heating technologies (
  • The cost of an ASHP varies depending on the size of heat pump, size of the property, whether it’s a newbuild or an existing property, as well as if you need to change the way you distribute heat around your property.  Typical costs are around £7,000 to £13,000 and it is recommended getting at least three installers to provide quotes to give you the best idea of likely costs for your home.
  • In terms of possible savings the figures below show the potential annual savings of installing an ASHP in an average sized, four-bedroom detached home, compared with the current heating systems listed (courtesy of the Energy Saving Trust website).
Old G rated gas boilerOld G rated oil boilerOld G rated LPG boilerOld electric storage heatersNew electric storage heaters
%d bloggers like this: