Hydrogen boilers or air source heat pumps?

A consumer guide to the future of heating

For UK households, the next 5-30 years will be a transition to one of a mix of possible renewable heat sources including ‘green gas’ boilers (biomethane/hydrogen) and air source heat pumps. If you are buying a brand new home in the next 1-5 years, it is likely to have an air source heat pump already fitted.

What does this mean for the 22.5 million households on mains gas boilers? We explain these new technologies, when they are suitable, running costs and what it means for you, in our guide to the future of domestic heating.

What is driving the future of heating? Our net zero 2050 target.

The UK Government has set into law an ambitious target to reduce all greenhouse gases to zero by 2050. Greenhouses gases from UK homes account for 20% of all emissions, so this is an important area for improvement.

Finding low carbon heat sources will be crucial to decarbonising the existing housing stock and heat pumps will dominate the energy transition for households.

The UK has a target for fitting 600,000 air source heat pumps per year by 2028.

Industry battle lines

The domestic heating industry is already gearing up for the changes with two clear ‘camps’ – those that manufacture and fit gas boilers and those that manufacturer and fit air source heat pumps. There is a great deal of work going on behind the scenes to push each technology as the natural replacement to gas boilers and gas boiler manufacturers are being investigated for greenwashing their products.

Gas boiler manufacturers, whose businesses have boomed over the last 15 years, are trying to secure their long term future, whilst heat pump manufacturers, an established technology but in it's infancy in the UK, have been given a green light to be the main replacement for gas boilers.

Hydrogen

Existing gas boiler manufacturers are developing ‘hydrogen ready’ gas boilers, but the reality is they still don't exist and studies have found them to be x6 less efficient that heat pumps. A recent NOA office report called on the Government to give clearer signals to households on the future of heat and bring forward the decision date on hydrogen for home heating from 2026.

All existing boilers are 'hydrogen-mix' ready, whereby they can accept a 20% blend of hydrogen into our existing gas supplies. You do not need to do anything or buy a new boiler especially. Indeed, buying a new boiler now will not future proof your heating system at all. It is best to keep your existing boiler going. Gas boilers should last 22 years and in the vast majority of cases you should not be persuaded to change your boiler any sooner.

We have considered the overall impact of the changes on households, industry and energy supply infrastructure.

More expensive to run

Whilst tests have found that 20-30% hydrogen can be mixed into our existing gas supplies and our existing boilers will still operate, it will require some infrastructure changes and an additional process to create the hydrogen. Overall the price for fossil fuels is likely to rise.

For a full hydrogen network, all supplies will need to be upgraded at a significant cost to the national finances. Fuel prices will rise (as much as x2-3 higher) to recoup this investment.

Greater national cost

The main barriers to hydrogen is the cost of a brand new national network to replace the existing gas pipe supply network. This will come at some cost, financially and environmentally. It will also require hydrogen production on a huge scale. The ‘carbon neutrality’ of hydrogen depends on how it is generated and also requires carbon capture and storage to achieve its renewable status. 56 independent studies have found no role for hydrogen in home heating.

Air Source

Air source heat pumps on the other hand are an established and proven technology. They run on electricity and for every unit of electricity they use they generate 2-4 units of heat energy for the home.

As electricity increasingly comes from green sources (wind farms and biomass fuelled power stations) so they are considered an excellent solution to decarbonising our homes.

It is worth pointing out that one barrier that does not exist is the assertion that heat pumps are unsuitable for older properties. The Carbon Trust state that the average UK home needs just 6kW of heat on a very cold day. Heat pump outputs range between 3kW and 16kW so can comfortably heat most UK homes. Modern heat pumps can also run at the same temperatures as gas boilers, so households don't need to massively insulate their homes or upsize radiators, although both help to reduce running costs.

More space is needed

The impact on consumers is disruptive if they need to fit a hot water cylinder (70% of gas homes have a combi) and they need to find space for the heat pump. A large external unit plus a fridge-freezer sized internal unit means we may have to give up our airing cupboard to a cylinder once again.

High temperature heat pumps and hybrid heating pumps (combining a gas boiler and heat pump) are solutions that will not require us to change our radiators and the Committee for Climate Change view both as transition technologies on the way to better insulating our homes.

At present the cost of a heat pump is on average £5k after the grant, but prices are dropping and are expected to continue to fall with increased numbers of installations.

Running costs

At present, electricity costs 27p per kW hour compared with gas at around 7p per kW hour. However the running costs can be in line with gas boilers because of the proportion of free energy they generate (providing they are set up correctly).

To encourage more people onto greener fuels, gas and electricity prices need rebalancing by shifting taxes off of electricity tariffs.

Skills gap

There are simply not enough trained heating engineers or air conditioning engineers to fit heat pumps at the scale needed. The roll out of heat pumps relies on up-skilling 60,000 domestic heating engineers and that is a huge undertaking made worse by the existing skills gap for condensing gas boilers.

The core problem is that 99% of installers are not trained in heating system design and this knowledge is vital to setting up heat pumps to run that their label efficiencies. 

Whilst gas boilers still work even when set up poorly and inefficiencies are disguised by cheap gas prices, heat pumps have a much smaller margin for error and get very expensive very quickly when the same casual approach to correct design and installation is applied.

Dense urban areas

According to the Committee for Climate Change's Sixth Carbon Budget, we will need to be fitting 1 million heat pumps a year by 2030 and deploying other transition heat sources such as hybrid systems. The overall outlook points towards decarbonised electricity as the key to decarbonising our homes. 

Heat pumps do require outside space which makes installation difficult for those in flats. It is expected that 1 in 5 homes will move to a 'heat network' whereby a large heat pump will serve a block of flats, an estate or even a whole town. Other heat networks might be served by waste heats from industry.