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Energy experts usually discuss things in a civilised manner and there is agreement on many of the key elements of what the UK needs to do to reach net zero carbon emissions.
But bring up the subject of how to decarbonise the 28mn households and the conversation can become distinctly heated.
Some 80 per cent of British homes have gas heating, but with existing gas boilers incompatible with net zero targets, the UK now seems to be leaning towards electricity as a cleaner option, to judge from remarks by Energy secretary Grant Shapps. Broadly speaking, that looks like the right idea.
It’s understandable that the debate about residential heating raises temperatures. The sector accounts for about a fifth of UK CO₂ emissions, so a credible strategy is crucial to achieving the 2050 net zero target. It also requires a huge mobilisation of resources: if we started now, we would need to switch something like 18,000 homes a week from gas boilers to hit the 2050 target.
The big sticking point is that cleaner, greener alternatives are — at least at the moment — significantly more expensive than good old gas boilers. It’s a significant factor in the lack of progress in switching.
While the decarbonisation of electricity is proceeding apace and electric vehicle sales are on the up, green heating is but a twinkle in the eye of energy-system modellers.
Only 412 of every 100,000 homes have installed heat pumps. Hydrogen powered heat, meanwhile, is very much at the trial stage. Two north Yorkshire seaside towns — Whitby and Redcar — are being considered for pilot projects, to the concern of some locals.
Comparing hydrogen power and electric heat pumps, the latter look like a miracle of efficiency, capturing heat in the air (or from the ground) even when it feels cold. For every kWh of electricity required to power them, they can provide some 3kWh of heat. Gas boilers produce 0.9kWh heat for every 1kWh of energy. Hydrogen heating is by far the least efficient, producing less than 0.6kWh of heat for every kWh of electricity used to make the hydrogen.
The benefit of this greater efficiency is masked by the current very high cost of electricity. But that includes a plethora of climate and non-climate policy costs. These reflect past decisions. But starting from where we are today, the cheapest way to decarbonise UK household heating is likely to be heat pumps.
Say they ran directly on electricity from UK wind farms at £50/MWh. That would be turned into heat at £16.6/MWh. Even adding in the cost of buying and running the heat pump, let’s say £40/MWh, that only adds up to some £50-60/MWh. The same figure for hydrogen is more like £150/MWh.
Given the difference, why does hydrogen heating even get a look-in?
The reason is “system” costs. Producing heat from electricity rather than gas will require a massive upgrade of the transmission and distribution grids, investments in storage and back-up power generation. These need to be added to the heat-pump side of the ledger.
Proponents of heating homes with hydrogen — which would largely be supplied via existing gas infrastructure — have argued that this may tip the balance in their favour.
It is much harder to test this argument. It is true that electricity grids will require a lot more investment than gas grids, £330bn compared to £43bn, on government estimates. But those new power grids will be delivering a lot of new electricity. On a per unit basis, this may balance things out.
An added complexity is that it is hard to separate out the network investments required for electric heating from those already pencilled in for, say, EVs. We also may not need as much grid as we think. “Smart” heating systems, which turn themselves on when the wind is blowing and there is capacity on the network, would reduce investment needs.
Indeed, most studies suggest that heat pumps will be a cheaper option for the country as a whole than hydrogen, which may end up limited to housing stock that is incompatible with electric heating.
If the government does plump for heat pumps, the next problem is adapting Britain’s old and draughty housing to technology that works best in well insulated properties. Nonetheless, it increasingly looks like hydrogen will have only a small role to play in the nationwide drive for net zero heat.
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