Air source heat pumps are not the answer

by | 6 Dec 2023

The Scottish Government is putting all its eggs into the air source heat pump basket. It is the wrong basket and it is going to fail.

First published in The Herald

Air source heat pumps are not the solution to decarbonising Scotland’s heat. I write these words not as someone who wants to delay climate action but greatly accelerate it – because there is a much better and more coherent alternative. The people of Scotland have been excluded from the debate about how we achieve our climate goals and instead we’re being fed half-baked ideas by politicians who want to persuade you they’re doing something.

First, air source heat pumps work. There are certain houses in Scotland where alternative heating options are not possible and, particularly in efficient new-build houses, heat pumps can work well. That isn’t the problem.

Heat pumps cost about £15,000 to install and on average last for about 15 years. You will quickly realise that this means you will pay £1,000 a year for the capital cost of your heating before you pay for electricity. That works out about the same as heating your house with standard electric radiators, which are long-lasting and reliable.

There are significant moving parts in heat pumps and so inevitably they will require regular maintenance. This is a specialist job, can be expensive, and we don’t have anything like enough maintenance engineers. To be planning a circular economy based on a carbon-intensive heating solution (making a heat pump emits about 1,500 Kg of carbon dioxide) that needs constantly replaced makes no sense.

And this is a massively expensive national project. The total bill for this is £33 billion. Since Scotland does not manufacture air source heat pumps, almost all of this money would be exported out of our economy. 

And that’s not the end of the bill because moving from gas to electric heating will require significant additional deployment of electricity generation and significant investment in the national grid to support it. (This is why moving to all-electric radiators is a bad idea because the additional load on the grid would be three times greater.)

It doesn’t even make sense as the first step, because currently about 40 per cent of Scotland’s total heat load is lost through leaky houses. We shouldn’t even be assessing the heating load needed for gas heating replacement until we get houses up to a sensible level of thermal efficiency.

When the Victorians built a sewer system they didn’t do it by telling every household to build their own 20 metres under threat of a fine

And it gets worse, because the way this is being rolled out is a case-study in how not to do things. At the moment we insulate one house at a time according to when the household can afford to do so. Then potentially at a different time we go back to the same house to fit a heat pump. Then at some point after that we go back to the neighbouring house to insulate – and so on.

Tackling climate change in this fragmented way comes with a very high cost premium – we calculate it at about £9,000 per household. It makes no sense, but this is happening because government is trying to push almost the full cost of decarbonisation onto the household. 

The Scottish Government has said that it is the private sector which will make the bulk of the investment. This is simply dishonest – it is the householder, you, who will make the investment and the role of the private sector is only to lend you money at commercial rates. That will quickly and substantially increase the inefficiency premium per household well beyond £9,000

And this is big money. Realistically the cost of universal heat pump installation with the additional investment in the grid it needs will be creeping rapidly towards £50 billion. Insulating all our houses will add £40 billion to that bill. This is major, major work, and the entire cost (with substantial added premium) is being pushed directly onto households.

When the Victorians built a sewer system they didn’t do it by telling every household to build their own 20 metres under threat of a fine. Can you see how daft this is? Decarbonisation is a major engineering project, not a DIY job.

There is a much better way to decarbonise our heating. It is called ‘district heating’ (or sometimes ‘heat networks’). It is basically exactly the same as the system that brings water to your house, but through insulated pipes because it is carrying hot water.

In your house you simply swap your gas boiler for an inexpensive, long-lasting, reliable heat exchanger. It takes whatever heat you need out of the heating mains and otherwise works as normal with the heating system you already have installed in your house.

It is disruptive; pipes have to be dug everywhere and pipes installed. But once it is done it will last, literally, for hundreds of years (the oldest currently operating system is over 100 years old already and going strong).

A politician who was serious both about Scotland’s economy and the need to fight climate change would be leading a debate that involved the people of Scotland instead of patronising them

Once that is done the heat can be supplied any way at all, anywhere at all within reaching distance of a network. Solar thermal (heat from solar) is very efficient and extremely cheap. So is heat recovery from mine works, rivers, industrial plants, our geology (one granite outcrop in Fife contains enough heat to heat the whole of Scotland indefinitely) and much more.

This gives you reliable heat forever – and it is cheap as chips once the capital is in place. The capital isn’t cheap, but then again at a cost of probably a touch over £50 billion it is effectively much the same cost as what is currently proposed, but you only do it once.

And if this work and the work to decarbonise homes is matched by a proper industrial strategy, Scotland could capture the majority of the economic gain. We could build very substantial industries in zero-carbon insulation materials made from hemp and we could redirect many of the supply chains in the oil industry to reorganise and produce the kit for district heating.

Common Weal calculated all of this. A very ambitious ‘Green New Deal’ for Scotland would cost about £175 billion in total. If you financed that all in one go and repaid it over 50 years (this is a multi-generational project if done right), it would cost about £5 billion a year to repay. But we modelled the impact on Scotland’s economy of capturing an achievable amount of the supply chain and it created over £6 billion in additional tax and other direct income as well as creating many tens of thousands of jobs.

Scotland cannot afford to get this wrong and we can’t afford to do it twice. Nor can we afford to alienate the people of Scotland over the work we must do on climate change by making it a terrible burden on them and not a massive opportunity for reindustrialisation.

Politicians who want to produce press releases and gain plaudits set targets and take easy solutions which make all of this someone else’s problem. A politician who was serious both about Scotland’s economy and the need to fight climate change would be leading a debate that involved the people of Scotland instead of patronising them. If that was done, the debate would very quickly sound like the words above.

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