Do Grid Constraints Make Borough Housing Plan 'Mission Impossible'?
Eric Leach looks at the capacity issues in local energy generation
Aging electricity sub-stations are vulnerable to fire. Picture: Richard Webb
May 6, 2025
Reports of another electrical substation fire in Maida Vale on 29 April should not surprise those who were aware of similar fires in Hayes and in West Ealing. The previous day massive power outages in Sapin and Portugal had again raised the issue of energy security.
More attention needs to be focused on electrical power capacity planning, substation maintenance and, mostly, about data centres’ massive appetite for electrical power particularly in West London. It also puts electrical capacity in the context of the Government’s super ambitious house building plans.
On Thursday 20 March this year at just before midnight an electrical substation fire at North Hyde, Hayes, Middlesex led to thousands of homes in Hayes going dark and Heathrow Airport shutting down for 18 hours. Even two weeks later, the organisation responsible for this substation – Scottish & Southern Energy Networks (SSEN) – had made no public statement about the fire and the power failure. National Grid claimed there were two other local substations each of which could have handled the power requirements of Heathrow Airport but the airport’s boss said it was not possible to ‘instantly’ switch to alternative power suppliers because of the re-start up complications of multiple airport services such as IT, baggage carousels, lighting, heating, air conditioning, escalators and retail.
It’s worth noting that all three organisations I have mentioned are privately held companies responsible to their shareholders and not responsible to electricity users or the general public.
In July 2022 the Greater London Assembly published a report called ’West London Electrical Capacity Constraints’. The North Hyde Substation is shown to be at 100% ‘Peak Capacity Utilisation in 2021/22’. Full capacity was also flagged up for parts of Ealing and Hounslow. SSEN stated that new large residential developments (over 25 housing units) in much of Ealing and Hounslow ‘will have to wait several years to receive new electrical connections’.
Shortly after the North Hyde sub-station fire, Heidi Alexander, Secretary of State for Transport, described the power outage as ‘unique’ and ‘unprecedented’. Just five miles east of North Hyde, Hayes in late afternoon 19 January 2024, I watched as an electrical substation burst into flames in the centre of West Ealing. The flames reached some 25 feet in the air. Shop lights and house/flat lighting were out for hours. SSEN admitted that the West Ealing substation fire was because of ageing infrastructure. Within weeks it had completely replaced the old substation.
Data centres are a fairly recent phenomenon in the UK with the first one opened by Barclays Bank in 1961. Data centres provide the power to facilitate ‘Cloud’ computing, online retailing, online banking and increasingly Artificial Intelligence services. The computers require 24/7 cooling.
Datacentermap.com estimates there are 404 data centres in the UK with a significant proportion operating in West London. On Slough Trading Estate there are 22 data centres (stantech.com). This is the largest data centre cluster in Europe. There are four in the North Hyde area of Hayes, and five in Stockley Park, Uxbridge. Two are up and running at Park Royal with another two (25Megawatts each) under construction there. There are 10 data centres in Berkshire.
The average energy capacity of data centres is around 25 Megawatts (MW) – with the very largest reaching 100 MW (statistica.com). Annual running costs vary between £10 million and £25 million (optrium.co.uk). The energy needs in West London of each of the larger data centres easily exceeds Heathrow’s total requirement of 40-60 MW (watt-logic.com). So, adding another runway and a sixth terminal would be much less challenging from an electricity supply point of view than 10 new data centres going live locally over the next 10 years.
On 26 March 2025 ‘The Times’ reported on Segro’s involvement in a £1 billion, 30,000 sq m data centre project at Park Royal. The completion date is 2029. Segro is a leading owner, asset manager of modern warehouses and industrial properties in the UK and Europe.
Much useful data can be culled from the SSEN December 2024 draft consultation report entitled ‘North Hyde Grid Supply Point Strategic Development’. The report lists a development and maintenance schedule. None of the project completion dates is earlier than 2027 and some are scheduled for completion in 2030. Drilling down to some of the detail, the report draws upon housing supply plans in Ealing Council’s outdated 2012 Local Plan (12,407 new homes, 2011-2026) and Hounslow’s similarly ancient 2015 Local Plan. Although residential tower blocks have electrical supply demands far smaller than data centres, the new Government’s target of 3,132 housing completions in Ealing every year to 2029 (totalling 15,660 new homes) will require significant new electrical infrastructure. Let’s postulate that 3,000 new homes each year in Ealing will be flats in 10 storey tower blocks (60 flats per block). That works out as 50 new tower blocks each year until 2029. A staggering five-year total of 250, 10 storey tower blocks.
And now let’s return to the substation fire in Hayes. A recently retired SSEN engineer a explained to me that old substations are susceptible to parts and materials’ failures and a single spark can ignite the significant volume of cooling oil in the substation. He said there were 100s of ageing substations which need to be replaced but SSEN lacked the manpower resource to carry this out rapidly. Unless arson, terrorism or cable and wire theft is proved by the Police, SSEN, National Grid or Government, it’s more than likely that the 20 March fire and airport shutdown was, another failure of ageing substation infrastructure.
In October 2024, the Government created a new ‘Independent Public Corporation’ called the National Energy System Operator (NESO). NESO’s main stated objective is to ensure security of energy supply. The Government has commissioned NESO to investigate the power outage at North Hyde. It seems NESO has a new collaborative arrangement with the GLA for strategic energy planning. Presumably, it will be NESO that carries out the complex balancing act of meeting the energy need of new data centres, expanding commercial and industrial organisations, millions of domestic energy consumers and the smooth transition to energy decarbonisation.
Taking the data contained in these reports we can conclude that electrical supply capacity planning for new homes is challenging in a situation where the target housing completion numbers change every few years. The new 2024 National Planning Policy Framework targets for annual home completions for the six West London boroughs (2024 – 2029) for West London comes to around 15,000. Over five years that comes to 75,000 completed homes and let’s say 1,500, 10 storey residential tower blocks. Probably reaching these totals is science fiction. If they are reached, providing the electrical power, new substation capability, networks, residential connections, and installation and maintenance manpower will all be mission impossible.
We don’t know if there is a reliable figure for new data centre projects in West London over the next five years. I have searched but I can’t find one. No national, regional or Local Authority targets. Also, when a Local Authority approves or rejects a data centre Planning Application this might affect neighbouring boroughs as the regional power suppliers territory will almost certainly include parts of multiple boroughs. Electrical suppliers such as National Grid and (for West London) SSEN are not even on the statutory list of consultees for Planning Applications.
National Grid made a profit of £4.7 billion in 2024. SSE made a profit of £2.4 billion. If these organisations were state owned the dividends paid to shareholders and the £7.1 billion profits could have been invested in the further development.
Eric Leach
Mr Leach retired in 2004 after 38 years in the computer business. He now scrutinises all major planning applications in Ealing for West Ealing Neighbours. In 2016 Ihe was appointed a Government Neighbourhood Planning Champion and from 2013-18 he created and chaired the Government designated West Ealing Centre Neighbourhood Forum which produced the West Ealing Centre Neighbourhood Plan. In the upcoming Government Examination of Ealing Council’s New Local Plan 2024 – 2039 he will be participating querying on the lack infrastructure capacity planning.
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