Fuel for thought.

Original Article
May 14th, 2024


Can hydrogen help the UK to decarbonise domestic space heating?

Authors: Johnnie Leather, Public Policy Researcher, MA Social and Public Policy
Dr Neil G Cutland, MInstP, Consultancy Director, Sava

Hydrogen is the most abundant element in our atmosphere, but can we harness its energy potential to heat our homes? At present, electric heat pumps are the government’s preferred low-carbon heating solution. In addition to this, there is ongoing research and testing to determine the role that hydrogen could play. With no carbon dioxide emissions at the point of end use, a case is being made to replace the natural gas burnt in our boilers with hydrogen. However – is the transition to hydrogen really that straightforward? Is hydrogen a better alternative to heat pumps? Or is it all hot air?

In accordance with the UK’s 2050 Net Zero target, the space heating of homes – which accounts for around 14% of annual emissions – will have to be decarbonised. To address this challenge, the upcoming 2025 Future Homes Standard is set to outlaw fossil fuel boilers in new dwellings, while a further ban on fossil fuel boiler sales is expected by 2035. With 83% of homes in the UK warmed by fossil fuel boilers, it is clear we are entering a heating revolution.

The hydrogen rainbow
Unlike the gas currently burned in domestic boilers, pure naturally occurring hydrogen gas, known as ‘white’ hydrogen, is hard to locate and extract. Therefore, the viability of using hydrogen to heat homes is heavily contingent on the availability of produced low-carbon hydrogen.

According to the International Energy Agency (IEA), in 2022 global hydrogen production relied heavily on the use of fossil fuels. Natural gas without carbon capture and storage (CCUS), resulting in ‘grey’ hydrogen, accounted for 62% of production. While ‘brown’ hydrogen from coal made up 21% and oil 0.5%. Following from this, by-product hydrogen, produced at refineries and in the petrochemical industry, amassed 16%.

Finally, the low-carbon options and therefore, the only ones being considered for space heating decarbonisation, represented the smallest share of production. Fossil fuels with CCUS made up 0.6% and electricity 0.1%. The hydrogen produced using these energy sources are also known as ‘blue’ and ‘green’ hydrogen respectively and will be referred to as so in this article.

 Figure 1: 2022 global hydrogen production by technology. Data sourced from IEA Global Hydrogen Review 2023

Hydrogen boilers
When it comes to burning hydrogen for heat in our homes, this can be done in boilers like those used for natural gas.

Hydrogen boilers come in two main types, the first being ‘hydrogen-blend ready’ boilers. These are the same as regular natural gas boilers, and through some minor changes, can burn a gas blend of up to 20% hydrogen.

Despite marketing by some boiler companies, ‘hydrogen blend-ready’ boilers are not a recent invention, with boilers being required to operate this way since the mid-1990s.

The second type is ‘hydrogen-ready’ boilers. Again, these can also burn natural gas, but by changing a couple of components can operate on a 100% hydrogen gas supply. Though not available yet, ‘hydrogen-ready’ boilers are in development, with industry estimating that they will be available from anywhere between 2023-2028.

In terms of cost, the available ‘hydrogen-blend ready’ boilers are no more expensive than natural gas boilers. Equally, the UK’s big four boiler manufacturers (Worcester Bosch, Vaillant, Baxi, and Ideal) have promised that ‘hydrogen-ready’ boilers will cost no more than their natural gas equivalents. 

The gas grid and the transition to hydrogen
To transport hydrogen to our homes, the proposal is to use the existing gas grid. Although no official decisions have been made on how/if this will happen, the most plausible transition would happen in the following stages.

The first stage would be to deliver a blend of hydrogen and natural gas. National Grid, who own the pipelines, have plans to introduce anywhere between 2% and 5% hydrogen to the UK’s gas blend by 2025.

Following this, the hydrogen content would progressively be increased until it accounts for 20% of the gas mix; estimated to happen by 2028 at the earliest.

The final stage of the transition would be for the gas supply to be completely hydrogen. However – complications arise when the level of hydrogen in the gas blend rises above 20%.

If the gas supply were to surpass 20% hydrogen, the metal pipes, valves, and pumps in the grid would be damaged, meaning they would all have to be replaced with ones made of alternative materials. Also, all boilers would have to be ‘hydrogen-ready’ not just ‘hydrogen-blend ready’.

Estimates place the earliest possible completion date for such tasks to be mid-2040s, so we are a long way off knowing the details of how such a change would happen, but both would undoubtedly be arduous and expensive.

It must be noted, that until 2026, the government are refraining from making a ‘strategic decision’ on the exact role that hydrogen will play in decarbonising homes. This means that prior to this decision, any comments on how and when hydrogen will be used to heat homes are speculative.

The government’s stance
As mentioned, ultimately the government is still undecided on the exact role of hydrogen in decarbonising UK homes and meeting net zero targets. However, as we draw closer to the 2026 decision, it seems increasingly likely that hydrogen will only be used to meet a small amount of heating demand.

In their 2021 report, UK Hydrogen Strategy, the government explored the potential role of hydrogen in achieving net zero. The paper recognised low-carbon hydrogen as an option for decarbonising heating in buildings, with the possibility for it to be a like-for-like alternative for properties using natural gas. The report also expressed that the feasibility of such is contingent on further research.

Currently, a range of projects are underway with industry, regulators, and other stakeholders to determine the cost, feasibility, and safety issues of using hydrogen for heating homes. Amongst these are plans to trial a pilot hydrogen town. Whitby was proposed as a pilot hydrogen town, but after a backlash from the town residents who were concerned about the cost and safety of hydrogen, the trial was scrapped. Redcar was also being considered for a pilot ‘hydrogen village’ but was again scrapped after there was inadequate access to locally produced green hydrogen.

The arguments in favour
Those in support of hydrogen heating are mainly gas distribution networks, boiler manufacturers, and energy suppliers. In the UK, these three sectors have joined forces under the guise of ‘Hello Hydrogen’, to raise households’ awareness of hydrogen’s role in reducing emissions.

One argument for hydrogen as a decarbonisation solution hinges on the similarities between existing heating systems and those required for hydrogen. The argument goes that because of these similarities, in most cases, the physical changes to a property that are required to install a heat pump and the corresponding heating systems are greater than that for hydrogen.

The most compelling support for hydrogen heating is the advantage the supply chain would have over heat pumps. With an already well-established boiler supply chain, comprised of many manufacturers and gas engineers, this system could more easily be adapted to hydrogen.

The heat pump supply chain, on the other hand, is in its infancy and has proven to be a limiting factor in the uptake of heat pumps. Nesta estimates that there are around only 3,000 heat pump engineers in the UK, this is far off the minimum 27,000 required by 2028 to meet targets, and the 120,000+ gas engineers certified through the Gas Safe Register.

The arguments against
Despite the arguments in favour of hydrogen heating, it is not without opposition. Jan Rosenow’s, Is heating homes with hydrogen all but a pipe dream? An evidence review provides perhaps the best singular documentation of the arguments against hydrogen heating.

In the paper, Jan Rosenow, Director of European Programmes at the Regulatory Assistance Project, and Honorary Research Associate at the University of Oxford, reviews the evidence presented by independent studies on hydrogen heating. Rosenow’s overwhelming conclusion is that hydrogen is more expensive and less green than heat pumps.

The main reason for the heightened cost and emissions of hydrogen is the production process. The bottom line is, producing hydrogen is energy intensive, meaning the costs are high and the associated emissions are contingent on the energy source or the use of CCUS.

Even in an ideal world with cheap, abundant renewable electricity it is simply more efficient to use the electricity to directly warm homes via heat pumps than to produce ‘green’ hydrogen for use in boilers. This means, it will always be cheaper and more environmentally friendly to opt for heat pumps.

To be specific, a study by the Hydrogen Science Coalition stated that to deliver an equal amount of heat to buildings, heat pumps require up to six times less electricity than hydrogen-fuelled boilers.

Furthermore, the other low-carbon option, ‘blue’ hydrogen, would cause the UK to remain exposed to and reliant on the volatile international gas market.

If this were not compelling enough to refute hydrogen heating, then consider the cost and complexity of building a gas system that can run on 100% hydrogen. A task that would require replacing thousands of pipes, pumps, and valves meters underground or even having to build an entirely new gas system.

The impartial National Infrastructure Commission (NIC) recently found in their five-yearly report that the cost of producing hydrogen is forecast to outweigh the greater in-building cost of heat pumps. The NIC estimated that in 25 years the price of integrating hydrogen heating in the UK’s energy system would be 18% higher than a mostly electric pathway.

Other uses for hydrogen
As explained, hydrogen is not cheap, easy, or green (most of the time) to produce. This means that there is a robust argument for reserving what low-carbon hydrogen we can produce for hard-to-decarbonise sectors, where green alternatives are limited. The most suitable sectors are transport, specifically shipping, and energy-intensive industry processes like steel and glass production. Using hydrogen in steel production would be an especially good use of hydrogen because steel is the predominant material used in wind turbines.

Another potential use for hydrogen is energy storage. Electricity is converted into hydrogen via electrolysis, and this hydrogen can then be stored and converted back into electricity using turbines when required.

Although hydrogen energy storage has a low round-trip efficiency (40-60%), it has the benefit of being one of the highest capacity and longest duration storage options. This unique offering makes it apt to store large amounts of excess renewable energy that can be kept over whole seasons. The demand for storage of this kind will only increase as the renewables share of the generation mix grows.

The realistic role hydrogen will play in heating
It is likely that over the coming years, hydrogen will begin to be used to help meet a small amount of the UK’s space heating demand. However, it is unlikely that hydrogen will contribute much further than this, with none other than BP – an oil and gas ‘supermajor’ – stating in their 2023 Energy Outlook that there is only a limited role for hydrogen in heating buildings.

Government targets reinforce this, with a goal to develop 5GW of low-carbon hydrogen production capacity by 2030, enough to heat 5.5% of UK homes. Given there is no guarantee that this generation target will be met and there are other competing demands for hydrogen, it is evident hydrogen could only meet a fraction of the UK’s heating demand.

One option is to use hydrogen to ‘top up’ domestic heating systems, where the main heat source is a heat pump and the secondary a hydrogen-fuelled boiler. The Climate Change Committee suggest this is a good option for buildings where full electrification is not feasible and to help meet peak demand on cold winter days.

Concluding thoughts
Although it is always worth exploring and researching emerging technologies, this should not draw away from investment in already proven ones. With it becoming increasingly apparent that hydrogen heating only has a small role to play in decarbonising space heating, it is important we pursue the already proven solution: heat pumps.

Johnnie Leather, Public Policy Researcher, MA Social and Public Policy

Johnnie Leather is a Public Policy Researcher. He has an MA in Social and Public Policy and carries out research on energy policy and sustainability in the built environment.

Dr N G Cutland, Minstp, Consultancy Director, Sava

Dr Neil Cutland, who joined Sava in 2022 as Consultancy Director, has spent his whole career as an energy and sustainability consultant. He specialises in low-energy housing in particular. Neil has held Directorships at sustainable built environment consultancy Inbuilt, BRE’s Low Carbon Housing Futures
Centre, TEAM Energy and previously at Sava during the 1990s (when our name was National Energy Services). Neil also set up his own company, Cutland Consulting Ltd, in 2010, where his clients included the energy regulator Ofgem, the NHBC Foundation, Hastoe Housing, Knauf Insulation, BEIS, DLUHC and many others. Neil is one of the authors of the BREDEM-8 and BREDEM-12 models and has contributed extensively to the development of
the SAP since its inception.