What are heat pumps & how can you use them?
During your investigation into renewable heating methods, you may have come across heat pumps and wondered what they are and how they work. In this article, we’re going to focus on air and ground source heat pumps, and explain how they work and what are the benefits.
What’s the difference between air and ground source?
Heat pumps work by taking the heat from an area and redirecting it into your home – think of it as a fridge, but in reverse. A fridge takes the heat from your food and pumps it into the kitchen, therefore keeping your food cold. Heat pumps take the heat from the ground, air or water and pump it into your house, keeping it warm.
Air Source Heat Pumps (ASHPs) take heat from the air through an outdoor unit, which looks like a large fan. This is then connected to an indoor blower unit, which distributes the heat throughout the house.
Ground Source Heat Pumps (GSHPs) use heat found in the ground and function through a series of underground pipework. This pipework will span a large area and will be connected to an indoor or outdoor unit, which then converts the heat to be used within the property.
Which is most efficient?
In general, GSHP systems are more efficient than ASHPs – around 10-25%. This therefore means that the long-term energy savings with a GSHP out-stack that of an ASHP, with the ground source heat pump’s longer life span boosting these figures even more.
How easy are they to install?
Ground source heat pumps require a lot of space for the underground pipework – if laid horizontally, you can expect to need to use an area at least twice the size of the property you’re wanting to heat, and for vertical installations, boreholes measure 30cm in diameter and up to 120m in depth will need to be dug.
This need for space can mean that your installer will be digging up your prized petunias – so it’s worth considering whether it’s an (albeit, temporary) sacrifice you’re willing to make.
Air source heat pumps require little space – the outdoor unit typically measures 1.5m x 1.5m and the blower unit is only as imposing as a combi boiler. Due to the outdoor location of the unit, it may be necessary to obtain prior planning approval – but in most cases installations will be classed as permitted developments (i.e. not requiring planning permission) and an accredited installer will be comfortable with any design specifications.
If you’re concerned about the space the unit will take up, modifications such as wall mounts and unit colour changes are a fantastic way to blend in your installation.
Are they easy to use and maintain?
In terms of operation, the two units are very similar and should come with user friendly temperature and timer controls, with more complex controls that can be set to your requirements by your installation engineer.
Annual service agreements are a great way to ensure that your unit (whichever you choose) is getting the correct amount of TLC. If you choose not to have a regular service visit, it’s wise to keep check on the pressures within the system, and contact your installer if you notice any sudden drops.
Many manufacturers offer warranty extensions for installations that have enrolled into an annual maintenance plan – by adding this layer of protection onto your system, you can rest assured that you achieve its maximum benefit.
How will this affect my wallet?
Due to the amount of external enabling works that need to be carried out, GSHPs are going to impact your finances a little more than ASHPs. Both systems run more efficiently at low flow temperatures which can mean you’ll need to increase the size of your radiators, and it’s common to couple the heat pump installation with underfloor heating (UFH) – although this would be an optional extra.
Typically for a three-bed semi, a GSHP will cost in the region of £10,000-£15,000 and an ASHP around £6,000-£9,000.
Once over this first hurdle, it’s important to remember that heat pumps are a renewable technology and come with their own set of government backed incentive schemes. The Renewable Heat Incentive (RHI) works on a domestic and commercial scale and pays you for having the system up and running.
The domestic RHI runs for seven years and when claimed against a ground source heat pump installation can fund between 80%-110% of the initial installation cost (although this can vary greatly depending on the groundworks cost). For air source heat pumps, you can expect to gain back between 70%-80% of your initial installation price.
Once this seven-year period is over, you can then benefit from the running costs savings for the remaining lifetime of the system. Against replaced oil or electric heating systems, heat pumps stack up well with utility costs savings and protect you from the ever-increasing prices of the ‘Big 6’.
Use a trusted and experienced installer
If you’re considering installing a heat pump, a knowledgeable and accredited installer will be able to guide you through the process and help decide which is best for you.