Heat pumps have been used as a way of heating homes for some years now. In fact, the very first ground source heat pump was developed in the late 1940s. Despite this, gas boilers have long dominated the market for home heating. But could things be about to change?

The last few years have seen a large increase in the number of homes being fitted with heat pumps instead of traditional gas or oil boilers. Research shows that the number of heat pumps installed in 2018 was around 20 per cent higher than 2017. But, according to BRG Building Solutions, 95 per cent of the UK’s heating systems are gas boilers either wall hung or floor standing, meaning these appliances still dominate the market. Heat pumps take up just under two per cent of the market in 2019.

However, this could be set to change in the future. In 2019, the government announced that any new build homes must not be connected to the gas grid from 2025. Instead, these homes should utilise low-carbon options and be ultra energy efficient. If this is to be the case, heat pumps could eventually become the norm in UK homes.

With this in mind, can a heat pump be retrofitted into an existing home and how difficult would it be to do this?

Heat pumps can be installed in almost any home, however there are some considerations that may need to be addressed, particularly regarding insulation. In order for a heat pump to work at its most efficient, your home needs to be well insulated to prevent as much heat from escaping as possible. A house that is poorly insulated will require a larger heat pump to make up for the heat loss, and this could cost more money to install and to run. This is why the government has introduced a ‘Green Homes Grant Scheme’ in 2020 to improve efficiency of properties with poor insulation.

Additionally heat pumps work more efficiently on lower temperature heating systems, such as with underfloor heating. Older poorly insulated houses may need higher temperatures than the heat pump can cope with to get the house warm.

A suitably qualified heating engineer would be able to advise you on what needs to be done in your home in order for it to be appropriate for a heat pump heating system. This could include upgrading the insulation so your home has cavity or solid wall insulation, loft insulation and double glazing. However, these fixes should be relatively easy to achieve and most homes have double glazing now as standard.

The other consideration is disruption. You will need to consider the type of heat pump you will have (ground or air source) and also where it will be located. Ground source heat pumps tend to be more difficult to install. If you have a large area of land, the pipes can be laid horizontally. If you only have a small garden, the pipes will need to be installed vertically in holes that are around 100 metres deep. If you’re thinking of having a heat pump installed in your home, an air source heat pump may be the better option as it’s easier to install with less disruption.

Finally, you should consider location. An air source heat pump unit, for example, will need to be installed outside your home. It should be in a place that you can access easily when you need to clean the unit, adjust its settings or have the heat pump serviced.

A suitably qualified engineer will be able to discuss all of these things with you and will help you to decide on the best system for you and your home. 

Can an air source heat pump be connected to an existing system?

If you’re considering having a heat pump retrofitted in your home, you may be concerned about how well it will function with the heating devices already in your home, such as radiators and hot water tanks. This is understandable as radiators have a relatively small surface area and may need to output a higher temperature than, for example, underfloor heating that has a larger surface area. Heat pumps can work more efficiently in this scenario. You should consider whether you want to have this installed at the same time as your heat pump or separately. Alternatively, to avoid lots of renovation work, you could have larger radiators installed as an alternative.

Heat pumps heat your hot water too, meaning your hot water tank won’t be redundant. It can still be used to store warm water for when you need it. The tank may need to be checked to make sure it’s suitable for use with a heat pump.

Can you add a heat pump to an existing boiler?

You may be wondering whether you can use a heat pump alongside a boiler to heat your home instead of choosing one over another. The answer is yes, you can. You don’t have to rely on just a heat pump to warm your home if you don’t want to.

When the weather gets really cold, for example around -10 ℃, a heat pump may struggle to pull enough heat from the air or the ground and therefore may not be able to bring your home up to the temperature set on the thermostat. While most heat pumps will heat your home even in temperatures of up to -20 ℃, this may not be very efficient. Instead, you could use your boiler on these really cold days. 

Can a heat pump be too big for a house?

When fitting a heat pump in an existing home, it’s important that it is sized correctly. A heat pump that is too small will struggle to heat your home to the required temperature, while one that’s too big might be more expensive to run and could waste energy.

Trying to size a heat pump yourself could be difficult. Did you know that the sizing calculations are partially based on the lowest temperature in your local area from that year? This is important because the coldest temperature can differ depending on where you are in the country. For example, Scotland is generally colder than southern England. If you live in Manchester, the heat pump will be sized based on a temperature of -2.6 ℃. At these temperatures, a heat pump is more than efficient and it’s likely that you won’t need a boiler to run in tandem with it.

When considering a heat pump, you can ask a professional heating engineer to come to your house to evaluate the building and calculate the ideal heat pump size for you and your needs.

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