It is widely expected that from 2035, households in the UK will be banned from replacing gas boilers like-for-like, although the use of existing gas boilers will remain unaffected until they reach their end of life. This will mean a slow transition from gas boilers to an alternative heat source in existing properties but would also make the fitting of gas boilers to new properties a little short sighted from the developer’s point of view.

Heat pumps have emerged as the most likely alternative to gas boilers and are already being fitted, or at least considered, by a number of households as a means of cutting down their carbon footprints.

Electric vehicles (EVs) are also the subject of a government push towards lower emissions, leading to its publicised nett zero target, but take-up has been slower than predicted due to high initial costs and fears of being caught out by a new technology which we are told is developing fast. Heat pumps unfortunately are suffering from the same problems. They are expensive to buy and fit and are still in the early phases of development.

A replacement gas boiler can be bought and fitted for around £2,000 to £3,000. In comparison an air source heat pump installation can cost from £8,000 to £15,000. Some suppliers are advertising heat pump installations from £3,000 but this figure includes a possible £5,000 government grant.

Until 2025, under the Government's Boiler Upgrade Scheme, homeowners who install a heat pump can receive a £5,000 grant however, just £450million of funding has been earmarked for the programme, which means in reality that only 90,000 homes in the UK will benefit from the scheme.

Prices are liable to fall as the installed base increases and the manufacturing cost per unit drops accordingly. As with electric vehicles, heat pump technology is still in the relatively early stages of development and as the technology develops, the performance of the product will inevitably improve. This means that a household which commits to installing a heat pump now may find that they are paying more for what will become a less expensive, more efficient product in a few years’ time.

On that basis, it could perhaps be prudent for a householder to postpone a commitment to either an electric vehicle or a heat pump. The equation changes however, when considering the installation of a heat pump based heating system in a new build property. When the property is designed around the use of a heat pump providing underfloor heating to the ground floor of a property and radiators to all other floors. At this stage the need for retrofitting a new, more efficient heating system to suit the heat pump becomes redundant and the heating system becomes an integral part of the new build. This will cut down the installation cost and the running cost of the system.

At the moment, heat pumps will take longer to heat your rooms as gas boilers can heat water in your radiators to around 75C as opposed to the 65C presently achieved by a heat pump. It is because of this heat difference that many installations pair heat pumps with underfloor heating. The area of an entire room floor is much greater than that of a traditional central heating radiator, sending more heat into the room than a radiator, although at the slightly lower temperature.

A heat pump works in a similar way to a refrigerator, freezer or air conditioning unit. An air source heat pump extracts heat from the air surrounding the property, while a ground source heat pump collects geothermal energy from the ground. This heat is amplified via a small compressor and transfers the heat to water which is then stored in a holding tank or used to heat the property. The units are fairly large and there is a certain amount of noise from the compressor as there is with your refrigerator, freezer or air conditioning unit and therefore most installations tend to be on the ground against an outside wall of the property.

Heat pumps can be installed on any type of property, provided that there is enough outside wall space to fit the unit, although ground source heat pumps are impractical for use in anything other than a ground floor property. It is common to see air conditioning units fitted to the outside walls or balconies of flats in warmer countries where air conditioning is in common use, so as air source heat pumps work in a similar way to air conditioning units, there is no reason why they cannot be fitted in the same way.

As with air conditioning, the smaller the floor area of a property, the smaller the heat pump will be required to provide adequate heating. This makes the fitting of an air source heat pump to an outside wall much easier for smaller properties or flats, where they can be fitted using wall mounted brackets. With all installations it is important to maximise the airflow around the unit and the manufacturer’s instruction should be followed by the installer. It should not be forgotten, that a heat pump installation needs an accompanying hot water tank to be available and smaller properties, particularly flats, may not have the space required.

The performance of an air source heat pump is affected by the outside temperature and will be less efficient during colder winter months. The average air source heat pump produces three units of heat for every unit of electricity it uses.  This is three times greater than a gas boiler. This rate drops to around two units per unit of electricity when the outside temperature drops below zero, which is still around twice as much as a gas boiler will produce, per unit of electricity.

If you live in an particularly cold area, your answer may be to get a ground source heat pump, which takes its heat from under the surface where the earth’s temperature will still be somewhere between 10°C and 13°C, even when the surface of your garden is frozen over.

In most areas of the UK, air source heat pumps will work well, although you will experience higher electricity bills in winter as they require more electricity to produce a given amount of hot water. Ground source heat pumps are less efficient overall but are less affected by cold weather, and both should work around two to three times more efficiently than a gas boiler.

There are still a number of caveats to consider when looking at installing a heat pump. The technology for the domestic market is still developing and the market in five to ten years may look very different, but one thing seems for sure. Heat pumps are the future of domestic heating systems.

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