On 27 June 2019, the energy and clean growth minister Chris Skidmore signed papers that committed the UK to reduce carbon emissions to effectively nothing by 2050. If we are to stand any chance of meeting this target, known as “net zero”, there is one enormous challenge that we will have to tackle: home heating.

Warming our homes is responsible for between a quarter and a third of the UK’s greenhouse gas emissions. That’s more than 10 times the amount of CO₂ created by the aviation industry. Around 85% of homes now use gas-fired central heating, and a large proportion of gas cooking still takes place. Greening this system is a huge challenge by any measure. But if recent reports are to be believed, there could be a simple and efficient way to do it: change from using natural gas to hydrogen gas.

Hydrogen is abundant in the natural world and according to its advocates could power the next generation of gas appliances cleanly and efficiently.

“The attraction of hydrogen is that for a lot of consumers, they wouldn’t notice any difference. Customers would continue to use a boiler to heat their homes in a similar manner to natural gas,” says Robert Sansom of the Institution of Engineering and Technology’s energy policy panel. He is the lead author on a study conducted by the institute called Transitioning to Hydrogen.

Together with colleagues, Sansom assessed the engineering risks and uncertainties associated with swapping our gas network to hydrogen. Their conclusion is that there is no reason why repurposing the gas network to hydrogen cannot be achieved.

That’s not to say it would be easy, though. Technological and practical hurdles exist because there is no blueprint for such a conversion: there is nowhere in the world that supplies pure hydrogen to homes and businesses. The UK would have to pioneer everything.

Interest in hydrogen as a way to heat homes began in 2016 with a report called H21. It was conducted by Northern Gas Networks, the gas distributor for the north of England, and looked at whether it was technically possible and economically viable to convert Leeds to 100% hydrogen instead of natural gas.

“They went into a lot of detail, from the hydrogen production plants right the way down to people’s homes,” says Sansom.

The report drew a parallel to the way the gas industry converted from town gas to natural gas in the 1960s and 70s. Town gas was a combination of hydrogen, carbon monoxide and methane. It was mostly produced from the distillation of coal and oil and had been used for the first 150 years of the UK’s gas industry. With the discovery of natural gas in the North Sea, which is predominantly methane, the UK undertook a nationwide programme to convert 40m appliances over a decade.

Whole streets would be converted at a time. Engineers would inspect the gas appliances, and then convert them. Simultaneously, the town gas was disconnected and the pipelines were purged with an inert gas. Finally, the natural gas was pumped into the system and the engineers would make sure each appliance worked correctly before moving to the next street along.

Some manufacturers are now so convinced that a similar thing can happen with hydrogen that they have already begun to develop new household appliances. In February, Worcester Bosch unveiled the prototype of its hydrogen-ready boiler. It would run first on natural gas and then, after a servicing visit, hydrogen.

Also working in hydrogen’s favour is that for the past 20 years, the gas industry has been systematically replacing the metal pipes in its “iron mains” network with yellow polyethylene ones. Around 90% of the pipes will have been replaced by 2030. This is good news for hydrogen because the gas reacts with the old metal pipes, making them brittle. But the polyethylene is safe.

“Effectively we started a programme of hydrogen-proofing our gas network without knowing we were doing it,” says Sansom, who found himself becoming more and more impressed by the concept. “From a personal point of view, I was very much on the fence when I kicked off with this work. But I found myself slipping down on the hydrogen side in terms of its viability as a low carbon alternative to natural gas,” he says.

But not everyone is convinced by this sudden interest in hydrogen. Richard Lowes of the University of Exeter Energy Policy Group says that until recently the received wisdom had been that heating would have to be electrified in some way to meet our climate-crisis commitments. “That has basically come out of years and years of technical and economic modelling to look at how you get to fully decarbonised heating in the UK,” says Lowes.

Switching heating from gas to electricity would mean relying on heat pumps. These use electricity to extract heat from either the air or the ground. In the case of an air source heat pump, it works like a fridge but instead of sucking heat out of a food compartment, it pulls it out of the air and channels it into the home, where it is used to heat water, which is piped to radiators for central heating, and stored in a tank for hot water.

But because this technology works at a lower temperature than existing boilers, it requires many homes to be much better insulated, or to have larger radiators, capable of delivering more heating power. For those who have switched to heat-as-you-go combi boilers, it will necessitate the reinstallation of a hot water tank.

It’s extensive work but worth it, according to Lowes, who has removed his own gas boiler and is now using an air source heat pump to heat his home. “It was a lot of work but my home and heating system are now a lot more efficient. It’s always warm, there’s always hot water and it’s basically the same cost to run as gas,” he says.

The third approach is called district heating. It envisages water being heated at a central facility using waste heat from industry or green sources such as solar power. The hot water is then delivered to many homes simultaneously through a network of heavily insulated underground pipes. Both methods can significantly reduce the carbon footprint of home heating but the downside is that they require extensive work to roll them out on a national scale.

District heating would require water pipes to be laid under homes, and the widespread use of heat pumps would necessitate the National Grid’s electricity circuits being upgraded. It is this kind of disruption that hydrogen’s advocates say could be avoided because much of the national infrastructure has already been upgraded. That argument cuts no ice with Lowes. “It seems a bit hypocritical for the gas industry to say we can’t dig up the roads when they’ve been doing it for the past 20 years,” he says.

He points out that although the consumer may not experience so much disruption, significant challenges for the gas industry remain. For example, the National Transmission System, which is the network of pipes that supplies gas from the coastal terminals to the gas distribution companies and other major users, is made of metal. This would need to be protected from embrittlement in some way before any switch to hydrogen could take place.

“Hydrogen is certainly not a silver bullet,” says Lowes. And if we get distracted by it, we could be getting ourselves into more trouble, missing the 2050 energy target altogether.

But if there is so much uncertainty with hydrogen, why is the gas industry, which funds many of the studies, pushing it so hard? According to Chris Goodall, energy economist and author of What We Need to Do Now for a Zero Carbon Future, it is a matter of survival.

“They do not wish for their industry to be eaten up by a switch to electricity for heating. So they are moving as fast as they can to persuade us about hydrogen,” he says. And it all comes down to how the gas is produced.

Hydrogen is not found on Earth in a pure state. Instead, it has to be extracted from other substances, and the best one to extract it from is methane – in other words natural gas. Hence, the gas companies could effectively keep their current operations running.

But the extra steps involved in extracting the hydrogen would push the price up. Additionally, the extraction creates carbon dioxide as a byproduct, so large scale carbon capture technology would need to be developed to prevent it escaping into the atmosphere. Although this is a technology that the UK will have to develop anyway in order to reach net zero by 2050, it will add to the cost.

But natural gas is not the only substance that contains hydrogen. Water does too, and the hydrogen can be freed by a process called electrolysis, which doesn’t create any carbon dioxide. To make it totally green, which is the ultimate hope, electrolysis could be powered by wind farms. At the moment, however, the price of such electricity is expensive, and that would push the price of hydrogen up still further.

Goodall hopes that the cost will decrease as technology improves, but warns: “You can be accused of mindless optimism just by saying this.”

The UK’s future energy landscape is without doubt a difficult realm to navigate. Perhaps the best route will be revealed by not pitting the various solutions against one another. “All three have strengths and weaknesses and I expect that there’ll be a major role for each as a replacement for natural gas,” says Sansom. Even hydrogen’s detractors acknowledge this. “As a niche technology it can have real value,” says Lowes. He goes on to paraphrase the Heineken lager adverts of the 70s and 80s, saying that hydrogen could potentially reach the parts of the country that other energy solutions can’t.

Goodall also sees a role for hydrogen to “store” energy generated from renewable resources such as wind and solar power. The idea is that in windy months, any extra electricity generated from renewables will be used to make hydrogen, which would then be stored. When there is extra demand on the National Grid, or a seasonal drop in the power produced from renewables, the hydrogen can be burned to produce electricity.

The truth is that all options for us to decarbonise our heating systems will require significant disruption and cost. And while government continues to deliberate, the clock ticks towards 2050.

“There is no need to wait. We can deploy stuff now that works fine,” says Lowes, referring to his own experience of changing his gas boiler for a heat pump. “The urgency of climate change means there really isn’t any reason to delay.”

Others believe that there is a role for hydrogen and think it is worth taking a little more time to consider. But there is one truth that everyone agrees upon. “None of this is easy. If anyone is saying to you this is easy, they are misleading you,” says Lowes.

Hydrogen-powered cars

Hydrogen can also power vehicles, but in a different way than it would heat houses. Instead of being burned, the hydrogen reacts with oxygen inside a device called a fuel cell. Electricity and water are produced. The electricity runs the car, the water drips from the exhaust pipe.

An attempt to switch to hydrogen vehicles in the 1990s was thwarted byelectric cars, which store their energy in an onboard battery. But a new push for hydrogen vehicles is coming from Asia. China, Japan and South Korea have all set ambitious goals to have millions of hydrogen-powered vehicles on their roads by 2030.

Toyota and Hyundai are both offering hydrogen vehicles in the UK, but there are currently less than 20 hydrogen filling stations across the UK, mostly clustered around the M25.

“It will be really interesting to see what happens,” says Lowes. But he himself is not convinced: “Hydrogen is much more expensive than electricity, and the car is more expensive than the electric vehicle.”