Air Source Heat Pumps (ASHPs)

Air source heat pumps (ASHPs) are often easier to install than their ground or water source alternative as they only require connection to the main water supply, an electrical connection and in some instances a refrigerant connection. This type of heat pump is ideal where space is limited as there is generally no need to bury pipes or be close to other energy sources such as boreholes, canals or large bodies of water. Air source heat pumps can be used in residential and commercial applications of all sizes including high rise buildings where the units can be installed on the roof or at ground level.

Ambient Loops

Beyond using water as the primary energy source from which heat is drawn, heat pumps can also be used in a closed water to water ambient loop, kept within operating parameters by a primary plant technology such as an air source heat pump or a gas boiler. Reverse cycle heat pumps can transfer rejected energy from one area to another within a space or a building where there is a requirement. Where there is not a demand for this energy, it is rejected from this internal loop into the external surroundings or stored within buffer vessels to be drawn upon when needed. These are growing in popularity within communal residential schemes, especially in city developments which can benefit from a low temperature network.

Hot Water Heat Pumps

Hot water heat pumps (HWHPs) are a low carbon technology for heating hot water and are designed to be installed within the dwelling itself. They consist of a ducted system to supply external air to an air source heat pump mounted on top of a water cylinder. The heat pump collects energy from the ambient air and converts this into heat, which is then transferred to the water within the cylinder, creating hot water to be used in the building. The remaining cold air is then discharged outside.

Hot water heat pumps are often used as part of a hybrid heat pump system; predominantly used in new build residential applications to provide hot water, alongside a separate electric or gas heating system. This makes HWHPs a highly flexible system with cost and installation benefits when compared to their larger heating and hot water alternative.

Ground source heat pumps (GSHPs)

Ground source heat pumps (GSHPs) use a series of ground loops to absorb heat energy from the ground. These loops can either be installed in horizontal trenches around one meter in depth, or vertically in a borehole. Boreholes offer a little less disruption to the surrounding landscape but may require a little more capital upfront for the installation. GSHPs can be better suited for new build developments where the need for external space, (to install the ground loop) and the internal space (for the buffer tank and water cylinder) can be factored in at the early design stages. They can also be installed in existing buildings where the space and geographical needs are met and disruption is not an issue.

Heat pumps and hot water heat pumps provide an efficient way to meet the hot water and space heating demands within a building. Compared to boilers with a typical Coefficient of Performance (COP) of 0.9, heat pumps can achieve a COP of over 2.0 for hot water and over 3.0 for space heating. The higher efficiency of heat pumps increases their cost-effectiveness. Achieving this target can be challenging. However, the specification of heat pumps will meet that challenge and can also help maximise efficiency and minimise running costs.

Heat pumps are reducing in cost as the market grows. The initial outlay can be offset by the government's Boiler Upgrade Scheme, launched in April 2022. This gives homeowners a grant of £5,000 towards the installation of an air source heat pump and £6,000 towards the cost of a ground source heat pump installed by an MCS (Microgeneration Certification Scheme) accredited installer. This scheme is expected to run for three years, leading to 2025. As with all government schemes, it is worth checking that it is still available and keeping an eye out for new schemes as the push to net zero carbon gathers pace.

The sound level air source heat pumps (ASHPs) produce will depend on the type, monobloc or split system, make and model of the unit. This must be no greater than 42 dB(A) (the noise level you would experience in a quiet library) under the Microgeneration Certification Scheme Planning Standards (MCS) before they can be allowed as permitted development. Some exterior ASHPs can have special noise reducing casings if they are installed in enclosed spaces where noise might be more noticeable, such as courtyards. Ducted ASHPs can be installed inside the dwelling as another way of achieving the required level of acoustic comfort.

Heat pumps can be installed in existing homes that undergo a deep retrofit. Where the fabric energy efficiency is high, low carbon heating technologies are a viable alternative to gas and can deliver hot water and space heating effectively.

Heat pump installers, like gas boiler installers, are trained to fit the equipment correctly in line with the manufacturer's guidelines, applicable industry standards, and regulations. So, heat pumps do not require specialist installers. Manufacturers of innovative low carbon technologies, such as ambient heat networks and hot water heat pumps, often design their systems to be pre-plumbed and pre-wired to optimise the speed and quality of installation.