Hydrogen boilers: what you need to know

Heating homes accounts for 17% of UK carbon emissions and 85% of UK homes are heated by a natural gas boiler. 

Two simple facts that create a conundrum: how do we effectively decarbonise home heating and reach the overall target of being a net-zero carbon emitting country by 2050 without the enormous logistical and financial undertaking of ripping out the infrastructure that heats most of our homes?

An oft-touted path to net-zero is the prospect of hydrogen fuel being used to heat our homes in place of natural gas. It would mean converting boilers to use a cleaner, greener gas fuel source, without such a large-scale retrofit. But hydrogen for heating is far from guaranteed to land consumers with an economical, comfortable deal.

A December 2022 government report titled 'The role of hydrogen in achieving Net Zero' debunked the idea that hydrogen is an easy way to decarbonise home heating. 

It states: 'Hydrogen could play a role in domestic heating, but the extent of its potential is still uncertain and looks likely to be limited rather than widespread. We are unconvinced its deployment will prove to be economically viable by the time the Government has said it will determine the role of hydrogen boilers, in 2026.' 

What are the alternatives to hydrogen boilers?

Meanwhile, electrical low-carbon heating systems, including electric boilers and heat pumps, are already available. Heat pumps are highly energy efficient and, when properly installed in a suitable property, will usually operate at lower costs than a gas boiler despite the fact that electricity is much more expensive per kWh. 

But these central heating solutions have limitations. Heat pumps, for example, are disruptive to install and require renovations in many UK homes to attain cost-saving efficiencies. You need to put in a lot of money up-front in order to start saving money on energy bills over the longer term. 

While hydrogen could have a place in the heating of the future, we'd warn against being taken in by marketing such as 'hydrogen ready' labels on boilers that seem to confuse consumers about how easy and likely the promise of a hydrogen transition is.

Need to replace your current boiler sooner rather than later? Read our boiler brand reviews to find the most reliable boiler brands

What are hydrogen boilers?

Boilers that can run on 100% hydrogen fuel are called 'hydrogen-ready'. There are no truly hydrogen-ready boilers consumers can buy today. 

What consumers can buy are 'hydrogen-blend ready' boilers, which are able to run with a mixture of 20% hydrogen fuel and 80% natural gas. 

Heating your home with 100% hydrogen would be much more complicated than just buying a 'hydrogen ready' boiler. Besides the fact that the national gas grid would need to support this, you would likely need renovations in your home. Specifically, you'd need to swap out your gas pipes for new ones.

Is a hydrogen boiler future-proofed?

The viability of hydrogen for home heating hasn't yet been proven. Trials have been proposed by government and gas companies to see if it works at a community level, but it's been difficult to get local consent for live experiments in real communities.

Consumers are yet to find out what hydrogen fuel would cost and what sort of infrastructural changes would be needed to pipe it into people's homes. 

A hydrogen boiler wouldn't be a seamless swap with your current model. Molecular differences in the gas means your pipes will need to be resized. 

Other renovations may be necessary, too. A safety report to support a hydrogen heating pilot in Whitby advised four-inch holes be added to participating homes for ventilation.

Because of uncertainty around the role of hydrogen for heating, it's not recommendable to buy a gas boiler on the rationale that it will 'become' a hydrogen boiler, or to forego other low-carbon heating technologies solely on the basis that hydrogen is around the corner. 

Read our insulation advice guides to see what bill-busting renovations are available and what you could save.

What will hydrogen boilers cost to run?

We don't yet know what a typical 'unit price' for hydrogen fuel would look like. But Imperial College London modelled that hydrogen would be three times more expensive than natural gas for heating.

That's about how much more expensive electricity is than gas today. But heat pumps, which are powered by electricity, can be 300% efficient or more, creating three times more heat than energy used, whereas a hydrogen boiler that works via combustion would not exceed 100% efficiency. So in that scenario, a heat pump would have the cheaper running costs.

It's clear that hydrogen wouldn't simply be a like-for-like swap for natural gas as far as costs go.

How much will hydrogen boilers cost to buy?

A number of leading boiler manufacturers have made a joint price-promise commitment that a hydrogen-ready boiler will cost no more than a gas boiler does today.

However, economies of scale means that this depends on the level of demand being as great as it currently is for gas boilers. Until the government decides on just how big a role hydrogen will play in heating our homes, and hydrogen-ready boilers start to appear on the market, we can't be certain on the price.

We do expect that upfront costs – for the boiler itself and installation – will be closer to that of a gas boiler (typically around £2,500 for a like-for-like combi-boiler replacement) than to the current price of a heat pump (typically £8,000 to £14,000). However the cost of heat pumps (including installation) is expected to fall. The aim is for their costs to be comparable to those of gas boilers by 2030.

How much does a new boiler cost? – find out how much you should expect to pay for different types of gas or oil boiler. 

How do hydrogen boilers work?

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. 

If you need a new natural gas boiler, find out how to get one with the least environmental impact using our guide on the most energy-efficient gas boilers.

Pros and cons of hydrogen boilers

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 the common option. 

However, retrofitting heat pumps into older properties with different heating systems can be costly and disruptive. This is the case where hydrogen boilers may be suitable, though again, this is to be proven.

Hydrogen boiler pros

• Familiar technology – a hydrogen boiler will be easy for homeowners to understand and use. They would operate and feel like traditional boilers.
• Reasonable upfront costs – likely to be more affordable to install than other solutions (such as heat pumps), based on current prices. 
• Can heat poorly-insulated homes – boilers can make radiators piping hot which isn't very cost-effective or energy efficient, but it gets draughty homes to temperature easily. But ideally homes move away from this style of heating to reduce fuel poverty.

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. 
• 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.
• Not free of disruption – hydrogen molecules are very small, so the pipes in your home would need to be changed to run a 100% hydrogen fueled system. 

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.

If your next boiler is gas or oil, read our shortlist of the best boilers to make sure you get a model from a reliable brand. 

When will hydrogen boilers be available?

There is currently no set date, but it is likely that hydrogen-ready boilers will start appearing on the market in the next few years. 

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.

The government is set to make a decision on the role hydrogen will play in home heating by 2026. In December 2022, the Science and Technology Committee released a report claiming that viability was unlikely to be proven by this deadline. 

What is blended hydrogen?

At present, domestic hydrogen heating is a pipe dream (no pun intended). While we are using natural gas, there's no consumer demand for hydrogen, which in turn means little hydrogen is produced. But if hydrogen isn't produced, how do we use it to decarbonise heating? It's a bit of a chicken-and-egg scenario. 

One solution, to help unlock this stalemate and catalyse hydrogen production, is introducing hydrogen in a small quantity to the existing gas supply. 

Dubbed 'blended hydrogen', this concept would involve mixing 20% hydrogen with 80% natural gas. All existing gas appliances are certified to run on a 23% hydrogen-blend, so introducing a mix at this proposed level would reduce carbon emissions by about six million tonnes a year (equivalent to taking 2.5 million cars off the road) without anyone having to replace their current gas boiler or appliances. 

Blended hydrogen pros

• Reduces home carbon emissions without the need to replace existing gas boilers and appliances.
• Helps open up the market for hydrogen by creating a demand for hydrogen production.

Blended hydrogen cons

• Only a maximum of 20% hydrogen can be introduced to the gas network without the need for gas boilers and appliances to be replaced.  
• Blended hydrogen reduces, but doesn't eliminate carbon emissions from the home. As such it is at best a short-term solution and a stepping stone on the path towards Net Zero. 

How hydrogen is produced

The potential benefits of hydrogen boilers are clear, but there are outstanding questions around how the hydrogen itself will be produced: 

How is hydrogen made?

Hydrogen can be produced in a number of ways, some of which are more environmentally-friendly than others, as the most common processes create carbon emissions during production. Different colour designations are used to indicate how a specific batch of hydrogen was made. 

Grey hydrogen

This hydrogen is made by reforming methane or natural gas. Carbon dioxide is produced during this process. It's currently the most common way of making hydrogen, and has the highest carbon emissions.

Blue hydrogen 

This uses the same process as grey hydrogen but the majority of the carbon dioxide is captured and stored before it’s released into the atmosphere.

The amount of carbon that is prevented from being released into the atmosphere varies, and depends on the quality of the carbon capture and storage systems used. The methods analysed in the Government's 2021 paper on hydrogen production costs claimed to be able to capture 90 to 96% of carbon emissions.

Currently, it is the easiest way to produce hydrogen that has lower carbon emissions than grey hydrogen. However, blue hydrogen isn't zero-carbon. 

And, like grey hydrogen, its production relies on natural gas. Because of this, many believe the focus should be on a greener long-term production method that doesn’t require natural gas: electrolysis.

Green hydrogen

Green hydrogen is made by splitting water using electricity. While this production method doesn't require natural gas, it's only zero-carbon if the electrolysis process is powered entirely by renewable electricity. 

However, this is currently expensive to do and will remain so until the UK's electricity comes mainly or solely from renewable sources. The Scottish government's 2020 hydrogen assessment predicts that, as green hydrogen matures, it could compete with blue hydrogen by the mid-2030s.

However, it is likely that green hydrogen, in the short-to-medium-term, will be more expensive per kWh than natural gas is today.

Turquoise hydrogen

Research into so-called 'turquoise' hydrogen by hydrogen technology company HiiROC uses a process called thermal plasma electrolysis to produce hydrogen from methane and natural gases, but with solid carbon as the waste product, rather than carbon gases. 

This solid carbon (also known as carbon black) can then be used for other purposes, such as enhancing soil or used in tyres and building materials.

What about homes without a gas supply?

In its 2021 Heat and Buildings Strategy, the government has proposed regulation to phase out fossil-fuel heating in homes that are off the gas grid from 2026. This is in the anticipation that most home owners will install a heat pump the next time they need their current heating system replaced.

The report indicates that 80% of homes are energy-efficient enough for a heat pump to be a suitable heating method. Find out more about what's involved in installing a heat pump with our expert advice on air source heat pumps and ground source heat pumps.

Another option for homes with no access to gas could be an electric boiler. Read our guide on electric boilers to find out if this would be a suitable solution for you.