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Hydrogen has been hailed as the ‘green’ gas that could be heating our homes in the future. We explain how hydrogen boilers work, the potential costs, and the pros and cons of hydrogen as a fuel.
Heating homes accounts for 17% of UK carbon emissions. To reach net zero by 2050, how we heat our homes is set to dramatically change over the next few decades, with a move away from traditional gas heating systems. Some low-carbon heating systems, including electric boilers and heat pumps, are already available. But these have limitations. Heat pumps, for example, are disruptive to install and simply not practical (or even possible) for many households. Where they are viable, they’re often prohibitively expensive (even allowing for financial support that will be available from April 2022).
However, as the deadline to get heating net zero gets closer, more low-carbon technologies are likely to appear on the market. One of the solutions we expect to see take off is hydrogen.
It’s a low-carbon alternative to traditional gas (which is known as natural gas) and, because it’s also a gas, could in theory be distributed using the same network. As most UK homes (85%) are already connected to the gas network, this could make hydrogen boilers a lower-cost, low-disruption alternative to an existing gas boiler. In this guide, we highlight what the future may hold for hydrogen-based heating.
What are hydrogen boilers?
Hydrogen boilers work exactly like current gas boilers, except the fuel is hydrogen instead of natural gas.
Hydrogen is the most abundant element. When it burns in pure oxygen, the only thing released is water.
Air isn’t pure oxygen, though, so using hydrogen as fuel in homes isn’t quite this clean. While there will be no carbon emissions, burning hydrogen will still produce some of the other pollutants that are a by-product of burning natural gas, such as nitrogen oxides (NOx), a group which includes the gas nitrogen dioxide (NO2).
NOx emissions are greenhouse gases, and contribute to climate change. Long-term exposure to high levels of nitrogen dioxide can also lead to increased respiratory harm. It’s possible to manufacture hydrogen boilers in a way that minimises NOx emissions, but regulations would need to established to ensure this happens by default. The need to create new regulations and procedures to mitigate unintended consequences and ensure that hydrogen boilers are safe and viable is part of the reason that they are not yet available. If and when these problems are addressed, and assuming hydrogen can be delivered to homes through the existing natural gas network, hydrogen boilers could be a low-cost, low-disruption option for many households.
Pros and Cons
As with all low carbon technology, hydrogen boilers will be a good option for some households, but not others.
As a general rule, heat pumps better suit homes that are energy efficient and well-insulated. From 2025, all new homes will have to be built with a low-carbon heating system installed. In such new properties, where the planning can take account of relevant costs and infrastructure, heat pumps are likely to be a good option.
However, retrofitting heat pumps into older properties with different heating systems can be costly and disruptive. In these cases, a hydrogen boiler is likely to be a far less intrusive option, and allow insulation upgrades to happen at a later date.
One thing that’s not yet certain is how the running costs will compare with alternatives. As of early 2022, electricity prices are extremely high due to market factors pushing prices up, so if hydrogen boilers were a reality right now they’d probably be cheaper to run than electric boilers. However, this may not be the case forever.
Hydrogen boiler pros
- Familiar technology – a hydrogen boiler will be easy for homeowners to understand and use.
- Low disruption – the existing infrastructure could be utilised, meaning hydrogen-ready boilers could be installed before any switchover.
- Reasonable upfront costs – likely to be more affordable to install than other solutions (such as heat pumps), based on current prices. However, we expect heat pumps to come down in price as their popularity increases.
- Can heat poorly-insulated homes – boilers can more effectively heat poorly insulated homes compared with heat pumps, so could provide homes to with a low-carbon option in advance of paying for expensive insulation upgrades.
Hydrogen boiler cons
- Hydrogen production isn’t carbon-free – while burning hydrogen to provide heat doesn’t create carbon emissions, certain methods of producing hydrogen do release carbon (see ‘How hydrogen is produced’, below). Truly green hydrogen is possible, but it’s expensive and needs 100% renewable electricity.
- Burning hydrogen produces other pollutants – such as nitrogen oxides. It’s possible to control these and keep them to a minimum, but legislation needs to be put in place to ensure these controls exist in all hydrogen boilers.
- Running costs likely to be higher than natural gas – hydrogen costs more to produce than natural gas, so it is likely hydrogen will initially be more expensive per kWh. Costs should come down as technology matures and hydrogen gets cheaper to produce, though.
- There are unanswered questions – the government hasn’t yet decided on how big a role hydrogen should play in heating homes in the future. This uncertainty might affect things such as the cost of hydrogen (or hydrogen-ready) boilers.
Part of the reason for the lack of clarity over the role hydrogen will play in domestic heating is that other sectors may need hydrogen more, especially while supply is relatively scarce. The need for decarbonisation is far wider than in our homes. Industries such as aviation, shipping and steel, where electricity is not an option, will need solutions such as hydrogen to replace natural gas as their primary fuel. Given that electricity is a viable solution to heat homes, some argue hydrogen should therefore play a smaller role in heating homes than natural gas currently does.
Boiler manufacturers have already built prototypes for hydrogen boilers, with many calling for legislation to make it law that all new gas boilers sold from 2025 onwards must be hydrogen-ready. There are still logistical questions that need to be answered before hydrogen boilers can come to market, the two biggest being: Can hydrogen be passed through the existing gas network? Can we produce enough ‘green’ hydrogen (see see ‘How hydrogen is produced’, below) at scale? The government is set to make a decision on the role hydrogen will play in home heating by 2026.
What are hydrogen-ready boilers?
Like ‘HD-ready’ was to televisions before there was any HD content to view, hydrogen-ready boilers can run on the existing natural gas supply and, when it becomes available, be easily converted to run on 100% hydrogen. This would allow hydrogen-ready boilers to be installed in homes before any switch from natural gas to hydrogen happens. This will cause far less disruption, and ensure households only need to replace their boiler when it breaks. The idea is that if and when your area gets switched from natural to hydrogen gas, an engineer will come and carry out a service on your hydrogen-ready boiler to convert it to run on hydrogen. This service should take about an hour and the industry is anticipating it will cost about £100. This type of roll out will require all households to have a hydrogen-ready boiler in advance of the switch, so that nobody is left without heating because their boiler isn’t suitable for hydrogen. The logistics of this will need to be taken into account when drawing up these plans.