Hydrogen boilers: what you need to know

Heating homes accounts for 18% of UK carbon emissions, and around 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 logistical headache of ripping out the infrastructure that heats most of our homes?

One option that's been suggested by people in the heating industry is the prospect of hydrogen fuel being used to heat our homes instead of natural gas. It would mean converting boilers to use a cleaner, greener gas fuel source. But hydrogen for heating seems increasingly unlikely 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 stated: '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.' 

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

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What are the alternatives to hydrogen boilers?

Meanwhile, electrical low-carbon heating systems that can be swapped into your existing heating system, 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 more expensive per kWh. 

Heat pumps that can be used in a wet central heating system (hydronic heat pumps) produce cooler temperatures than boilers. So installing them for the first time in a home can come with additional work to make sure you'll get the temperatures you want. You might need better insulation, bigger radiators or underfloor heating, for example.

Find out more about heat pump costs and savings and read our guide to air source heat pumps explained

What are hydrogen boilers?

Boilers that could in theory burn 100% hydrogen fuel are called 'hydrogen ready'. Truly hydrogen ready boilers consumers aren't something consumers can readily buy at the moment. 

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.

Are we likely to be able to use hydrogen boilers in the future?

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 would 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, we don't recommend buying 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. 

If your boiler is on the blink and you're not ready for low-carbon alternatives, head to our guide to how to buy the best boiler and see our boiler brand reviews.

Would hydrogen boilers be expensive 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.

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 would hydrogen boilers work?

Hydrogen boilers would work exactly like current gas boilers, except the fuel used would be 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 it doesn't emit carbon, burning hydrogen still produces 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 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.

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 of fuel is far wider than in our homes. Industries such as aviation, shipping and steel, where electricity is not an option, will need fuels such as hydrogen to replace fossil fuels in the coming decades.

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.

When will hydrogen boilers be available?

It is likely that hydrogen ready boilers will start appearing on the market, but be wary of this claim – it's still no guarantee that hydrogen will ever be piped into the mains gas network. 

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?

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. 

In 2024, Worcester Bosch committed to change how it markets its hydrogen-blend ready boilers following a Competition and Markets Authority (CMA) investigation. 

The CMA was concerned that Worcester Bosch’s claims could give the false impression that consumers would reduce their carbon footprint and ‘future-proof’ their heating system by buying a Worcester Bosch boiler on account of it being ‘hydrogen-blend ready’.  But a consumer would be in the same position with other boilers on the market and, most likely, the one currently in their home.

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. 

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