Can the national grid take heat pump and EV Scotland?

Already it is straining. In many parts of Scotand and the rest of the UK, the grid has limited capacity and constrained, where a heat pump might represent a connection too many.  

As Andrew Ward, CEO UK Retail at Scottish Power has put it: "Grid capacity is an issue already in places across the UK. There are streets, for instance, where the grid can't take the addition of heat pumps because already homes have had fast chargers installed. There are areas in Glasgow where capacity is an issue. In St Andrews there is limited capacity.

“The need," he said, "for greater local grid capacity is why you will soon see us digging up roads, in for instance, Edinburgh this summer, as we invest billions to make sure the grid is ready for people when they want to make the change."

The impact of grid capacity on heat pump roll-out is mentioned in some of the Local Heat and Energy Efficiency Strategies that local authorities have created as the beginnings of an effort to define where there will be heat pump homes, and where heat networks. 

The Perth and Kinross LHEES, for instance, notes that while “Kinross and Milnathort and Coupar Angus have high concertations of "properties that are heat pump ready”, they have “limited spare grid capacity”.

Edinburgh's delivery plan lists 10 target areas with the greatest potential to migrate to heat pumps, but notes that other factors are “pressures on the electricity grid” and the “existing electricity price regime".

A massive programme of grid reinforcement and expansion has already begun, with the National Grid unveiling plans to invest over £60 billion. Yet there are still doubts over whether it will be able to take the mass shift to electrification.

A 2022 Department for Business, Energy and Industrial Strategy report estimated that UK demand for electricity is expected to increase by 2035 and double by 2050.

That increase in peak demand, it said, would be largely driven by heat and transport sectors. “An inability of the electricity distribution network to cope with such an increase could delay the decarbonisation of domestic heating and other key sectors of the economy.”

Read more: Heat pumps: Myths, truths and costs – find all articles here

It also noted: “Transmission network constraints are expected to become more significant over the next decade.”

In Scotland, and the rest of the UK, domestic electricity demand is at its highest in winter, with daily peaks in the morning before people leave for work, and in the evening when they return and switch on the oven, television and other appliances.

The grid therefore needs to cope with a number of things. It needs to handle the winter when the sun doesn’t shine so much, as well as long lulls in the wind. But it also needs to handle the daily peaks and troughs of demand. For the former, large scale storage solutions are needed, from pump storage hydro to solutions involving hydrogen, but for the latter some of the solutions lie in the home.

The way that may work is something Pat Hackett, one of the heat pump owners we visited, is interested in. He has been experimenting for himself with how he, through battery storage and shifting his own demand can help the grid - particularly around the 4-7pm evening peak.

“I want to see if, as an individual home, I can do it," he said. "Can it be solved for a house like this? If it was scaled up, would we need to dig all those roads up? And the answer, I've concluded,  is no. The grid system we’ve got now can deal with that fluctuation."

"I want," he described, "to work with the grid. I want to interact with it - so the grid can borrow from me, and I can borrow from the grid. That 4-7pm energy demand is huge. It wouldn’t matter if you have all the solar, all the wind, all these storage problems, we’ve still got to supply that. So we have to switch the load.”

Pat Hackett with his battery and energy app

Part of the answer, he said, lies in the heat pump, battery and solar combination he has installed. The heat pump allows him to distribute heating in a different way throughout the day, with solar he can charge the battery and store energy that might be used in his home or delivered to the grid.

Mr Hackett's experiment obviously revolves around just one house, but it does give an insight into the way the technology inside homes may provide some of the solutions to grid issues. 

The kind of storage and smart manipulation of demand that is achievable in homes is also something that a study by a team at the Energy and Power Group at the university of Oxford, has looked into.

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It found that if just 10% of British households switched to heat pumps it could increase peak electricity demand by 4 to 5%. Other studies has predicted as much as 7%. To cope with this, it  proposed a “flexible heating system”.

In this kind of system, explained researcher  Jesus Lizana, “new heating systems are integrated with heat storage, smart controls, and programs (or tariffs) that fairly reward and incentivize households to shift energy consumed for heating.” A key element in the system, it proposed, were heat batteries. 

This kind of approach is also one that Robin Parker, mission manager for Scotland at the innovation think tank, Nesta, could have a significant impact on grid peak demand.

Nesta recently conducted a pilot project with the Centre for Net Zero to investigate how heat pumps can be used more flexibly – shifting use away from peak times – using automation to control usage in order to better support a low-carbon electricity grid.

“The provision findings from this,” he said, “suggested that it was possible to shift electricity usage to different times in the day and that most households in the trial were happy to have their heating automated to manage demand. We are currently in the middle of a larger scale trial to follow up on and validate the findings.

“Another option," he said,  "for households is to have more and better storage – of electricity and of hot water – through storage batteries and bigger water storage tanks.

But some of this will be on a larger scale. Mr Parker said: “Storage capacity at the moment in the grid is for short term spikes at peak times. In the longer term, we will need long-duration storage, for example generating power in the summer and storing it to use in the winter – countries such as Denmark are already storing hot water over summer in huge quantities.”