Natural gas or green hydrogen heating? It’s not that simple

Given that almost 40% of global energy-related greenhouse emissions stem from buildings and nearly 30% of those from heat and power, it’s clear that cleaning up the way we heat our homes and workplaces is an urgent priority. How that should happen, though, is a topic that continues to stimulate robust debate.

There are many different approaches and technologies that are either already available or under development which promise to bring substantial benefits. The danger is that this plethora of options brings analysis paralysis. Governments, industry and consumers may be tempted to delay taking certain decisions now, for fear that this may preclude another, more impactful course of action a little further down the line.

But we don’t have the luxury of being able to wait to see which green technology proves the most effective in the long term. Our climate goals are necessarily urgent and ambitious; Germany, for example, has committed to reducing its heating sector emissions by a further 40% on current levels by 2030, compared to 18% over the last decade, while the UK’s recently published Heat & Buildings Strategy aims to achieve substantial carbon reductions from heat in buildings during this decade in order to reach net zero by 2050.

Success depends on our ability both to get people on board and to optimise the whole energy system; a narrow focus on sectors or heating technologies in isolation is a cul-de-sac. At the same time, we really need to understand the issues in full, within the context of the entire energy system. Partial analyses and isolated measures, for example focussing on enduse energy efficiency of products alone, are unhelpful.

The built environment is heterogeneous; there are no general-purpose solutions. A one-sided focus on switching to electric heat pumps, for example, ignores the technical and economic hurdles involved, as well as the overall load imposed on the energy system. In Germany, where the electricity supply is transitioning from coal and nuclear to wind and solar, it has been shown that a mix of electrons and green molecules offers the best solution for heating. This is despite the fact that, on paper, heat pumps have a better enduse efficiency than a boiler run on green molecules.

One reason for this is that each heat pump adds load that must be covered by the electricity system, including in periods of low wind capacity. Energy demand in the heating sector is characterised by seasonal variations when winter energy demand will be three to four times higher than summer, plus rare periods of extreme cold (‘1in-20 winters’). While gas infrastructure is designed to meet peak demand, seasonality represents an enormous challenge for national power supplies once heating is electrified, even if efficiency is optimised. It is therefore better to reinforce gas and electricity infrastructure in tandem, rather than remove gas connections to buildings in favour of electricity.

We need a balanced mix of energy sources and technologies to meet the current and future needs of all users, while also ensuring we move forward on all fronts rapidly and simultaneously. In practice, that means a combination of decarbonised electricity and decarbonised heating fuels, including hydrogen. This clean gas requires fewer adaptations to infrastructure and appliances than other green fuels and has the potential to be entirely carbon neutral. It’s also relatively easy to transport and store, meaning it can be exported from regions with the right climatic and geological conditions to generate the renewable electricity used to make green hydrogen, and carried to the consumer via existing gas pipelines. And it can be blended with natural gas for use in conventional boilers.

Using existing gas infrastructure in this way means hydrogen can reduce the total cost of heating decarbonisation, reducing financial burdens on households and governments and making it more accessible to low-income groups. For all these reasons, hydrogen can make a significant impact on greenhouse gas emissions from heating almost instantly, with minimal expense and disruption. And, on the other side of the coin, the heating sector can provide immediate security for investments in hydrogen production, transport and distribution, bolstering its ramp-up in other industries. In Germany, the gas grid can already directly absorb about 70% of the government’s 2030 volume target for domestic production of renewable hydrogen. Governments everywhere should today consider mandating boilers that can accommodate a minimum 20% hydrogen element in the gas they burn.

Renewable hydrogen is now widely recognised as a crucial building block for achieving climate goals, complementing efficiency measures and other renewable energies. And the ramp-up of the H2 economy is gaining pace: the EU and UK alone currently plan to generate more than 115 GW of electrolyser capacity for clean, electricity-based hydrogen by 2030 - and this is just the start.

Given the rapidity of developments around green hydrogen in recent years, it is perhaps unsurprising that there are still some unknowns around its overall costs and potential impacts. More research is urgently needed. However, it is already clear that policy makers should be seeking to provide flexibility to optimise the hydrogen value chain and the overall energy ecosystem. That means keeping our technology options as open as possible and remaining mindful of all the numerous, evolving and occasionally counter-intuitive factors at play.