Heat pumps - the facts

Read some facts from a local Hungerford resident with experience of installing heat pumps at home and for community buildings.

The Environment Delivery Team , 12 October 2023 11:00

John Downe by the Hungerford Hub and Library air source heat pump which replaced the previous gas boiler.

In this blog we hear from local Hungerford resident, John Downe, who shares his experience and knowledge of heat pumps. Through his active involvement in Hungerford Environmental Action Team (HEAT), John is keen to share with others how we can make changes to reduce the environmental impacts of our day to day living. We are grateful for John's insights here into the world of heat pumps.

In 2019 we installed an Air Source Heat Pump (ASHP) in our newly built home after a lot of research on the running costs and environmental impact of different approaches to provide space heating and hot water. As a result of the knowledge gained, I have been able to assist others on the subject and have been closely involved with installations of two further ASHPs in a 1970s 3 bedroom detached house and the more modern Hungerford Hub and Library building. With colleagues from the Hungerford Environmental Action Team (HEAT) we ran a successful Home Energy Show in September 2022 which, among other things, made a lot of information on heat pumps available to attendees (and subsequent YouTube watchers of the videos of talks) - you can find out more on the HEAT website.

How do heat pumps work?

We are all very familiar with heat pumps as you probably already have at least one in your kitchen - yes, the humble fridges and freezers we've known all our lives! A fridge has a simple job to do: move the warmth from inside the fridge to the "radiator" mounted on the back of the appliance. Even though the inside of the fridge is kept as cool as a very cold winter day, that radiator, almost magically, is always warm!

So, when that same mechanism is called a heat pump and is installed outside, then even on the coldest winter day it is able to extract warmth from the air to heat water for radiators or underfloor heating pipes. Instead of burning gas or oil to provide our heating and hot water, the heat source is the equivalent of the fridge radiator and is powered by electricity.

What's so good about that?

The good thing about electricity is that 40 to 50 per cent of what the grid supplies is sourced from renewable, low carbon sources such as wind, solar and nuclear; as the grid further decarbonises over the next few years, as is planned, that zero-carbon share will grow towards 100 per cent.

The other great thing is that for every kilowatt-hour (kWh) of electricity used by a heat pump around 3kWh's worth of home heating is produced (300 per cent efficient) whereas a gas or oil boiler will typically produce about 8 or 9 tenths of a kWh for each kWh of gas or oil supplied (80 to 90 per cent efficient). This means that providing a unit of heat to your house today with a heat pump reduces greenhouse gas emissions caused by your heating by two-thirds or more and will continue to do even better.

They cost a lot to run, don't they?

At current energy rates for most households (Ofgem/Government rates are gas 8p/kWh, electricity 30p/kWh as at August 2023), using an ASHP will mean running costs similar or lower than gas or oil - particularly if the mains gas can be disconnected to eliminate the daily standing charge. However, the Government has stated that by the end of 2024 the relative prices of fossil fuels and electricity will be significantly "rebalanced" to make ASHP running costs much more attractive (see "Powering Up Britain" from Grant Shapps, Minister for Energy Security and Net Zero).

But they're expensive, I can't afford one

At the moment, the installation of an ASHP and any associated enabling works should qualify for the £7,500 Boiler Upgrade Scheme (BUS) grant from the Government when replacing other forms of space and water heating - and as a bonus these works do not incur VAT either. 17,000 of these grants have been awarded so far out of a money- and time-limited scheme. These incentives can make a significant difference to the installation cost. Once energy prices are rebalanced as mentioned above, I think it is likely that the supply of £7,500 BUS grant vouchers will quickly be exhausted. Several mortgage lenders are also offering better terms for home energy measures like heat pumps.

What do I need to do to get one?

Ideally you will need an outside space close to your home of about the size needed to park a small motorbike. Inside the house (or in a loft) you will need a space for a hot water tank - like the 'airing cupboard' many houses used to have. Often existing radiators or underfloor heating pipework will be sufficient, but some radiators may need to be replaced with higher output ones. This is because, to optimise efficiency, with an ASHP the temperature of the water flowing in the radiators is lower than with gas or oil and therefore a greater area of radiator is needed to heat your rooms.

To qualify for the BUS grant your home's Energy Performance Certificate (EPC) must show that your loft and wall insulation is satisfactory.

If you decide to get quotes for using the £7,500 BUS grant to upgrade your existing boiler to a heat pump, I recommend that you contact local independent heating engineers who have the appropriate qualifications and approvals (see the BUS Government website) or go to one or more of the national energy providers who are now offering heat pumps on very attractive deals.

Anyone providing a tailor-made quote for your home will need to carry out a Heat Loss Survey to work out the amount of heat needed to keep each room warm even on the coldest winter days. This allows them to work out each room's radiator requirements and thereby the total ASHP heat output to keep the whole home warm and provide hot water. Some suppliers may well do this exercise in two parts with an initial no-charge estimate followed by a full survey/quote for which they may charge a fee.

Should I get one then?

From what I have learnt, I am confident that most homes with cavity insulated walls, an insulated loft, double glazed windows and is reasonable draught-free should be able to be heated comfortably and economically using an ASHP. Very good results can also be achieved in older properties, given a thorough Heat Loss Survey assessment to properly size the heating needed. If you have an ageing oil or gas boiler, now is the perfect time to include the low emissions, future-proofing option of a heat pump.