When we finally move away from fossil fuels, we’ll be left with a system of pipes that measures at least five times the circumference of the globe in length. Will we re-use it, repurpose it or simply decommission it? 2024 is the year we’ll tackle the big question of what to do with the gas grid.

Underneath your feet is a quiet marvel of engineering. It snakes around the country for over 284,000 kilometers and 85% of British homes rely on it daily. But by 2050, the gas grid may be completely obsolete.

To combat climate change - and meet the UK’s legally binding net zero target - we need to phase out fossil fuels right across the economy. For British homes, that means heating and cooking without natural gas.

Could we simply replace fossil gas with a low-carbon alternative? Possibly - and that’s what gas networks and boiler manufacturers have been arguing for, promoting hydrogen, which does not produce carbon dioxide when it’s burned, as a like-for-like switch.

But hydrogen’s prospects for wide-scale use in home heating are looking increasingly slim. The National Infrastructure Commission was unequivocal in its recent report, that: an energy system with hydrogen heating would be around 1.2 times as expensive as one without, and as such there is ‘no public policy case’ for the former. While the UK government’s official line is that a decision on hydrogen heating will be taken in 2026, Energy Minister Lord Callanan has signaled that its role is likely to be limited. (We’ve also written about why we don’t think hydrogen is the right solution for homes.)

So if it’s not used for hydrogen, what happens to the gas grid? Turning it off isn’t as simple as it might initially sound. Unused pipes can’t simply be abandoned - they need to be made safe. Decommissioning the grid could cost up to £25 billion in a ‘low hydrogen scenario’, according to recent analysis.

This opens up some thorny questions about who pays. Gas networks are privately owned, regulated assets. This means their value is set through a regulatory process, and the costs of maintaining and upgrading them is recouped from bill payers. At the moment the regulatory value of the gas grid is still increasing, because of ongoing investment in upgrading old pipes. But as homes start transitioning away from gas, these costs could be shared between fewer and fewer people.

It also poses some crunchy coordination challenges. Imagine a street of terraced homes, with a couple of large detached properties at one end and a block of flats at the other. Over the next 10 years, some owner-occupiers choose to replace their boiler with a heat pump when it reaches the end of its life. Then a small heat network is built and the block of flats connects to it. By around 2040, fewer than half the properties on the street use the gas network.

At some point, it might become unviable to serve this street with gas - but homes can’t be left without heating. This suggests that someone’s going to have to take responsibility for switching them to another heat source, ensuring that all households know when it’s coming, have time to prepare and can get a new heating system in place, with support if needed.

This type of planning and rollout isn’t beyond the realms of imagination. A highly coordinated approach was used to switch British homes from ‘town gas’ to natural gas in the 1960s and 70s. More recently, the switchover from analogue to digital terrestrial TV in the 2000s gives some pointers as to how a planned switch could take place. (Perhaps surprisingly given Britain’s recent track record in delivery, both of these programmes were completed broadly on time.)

More intriguing is the possibility of repurposing the grid, or parts of it. Could gas pipes, for example, be used to transport water which could in turn serve as a source of heat for heat pumps, or be used for compressed air energy storage - a means of storing electricity in power grids? Could they transport electricity cables? Could we imagine other ways to breathe new life into these assets - rather than simply stranding them?

2050 might seem a long way away, but we have to take decisions on the future of the grid pretty soon. Little serious planning has been done so far, but expect that to change in 2024.