Hounslow Council has approved a new data centre on a 12.2-acre brownfield site at the Haslemere Heathrow Estate, requiring an 80MVA high-capacity electricity connection.
That connection would be enough to power tens of thousands of homes, underlining the enormous energy appetite of modern AI-focused data centre facilities.
The approval has prompted a warning from energy regulator Ofgem, which says speculative projects risk blocking viable investments from connecting to Britain’s electricity grid.
“The connections queue must work for consumers and for projects ready to invest, build and connect,” an Ofgem spokesperson told City AM, adding that speculative schemes delay viable projects and create uncertainty for network planning.
“That’s why we’re consulting on a new data centre commitment fee and stronger commitment requirements, helping free up capacity and speed up connections for projects that will deliver for Britain,” the spokesperson added.
Ofgem confirmed that simply securing planning permission would not allow a data centre to bypass the proposed tougher rules, which could require developers to meet additional milestones and pay an upfront fee to hold their place in the grid queue.
Applications for new data centre grid connections more than tripled from 41GW to 125GW between November 2024 and June 2025, with data centres accounting for at least 73GW across 315 projects.
The Greater London Authority has said around ten times as much electricity capacity as that currently used by existing London data centres has already been requested through the grid connection queue.
There were 99 operational data centre sites in London and another 26 in the planning pipeline as of November last year, according to the GLA, with the capital accounting for around 80 per cent of UK data centre capacity.
Hounslow councillors were told the Heathrow development would draw electricity through the Laleham Grid Supply Point, outside the borough, and would not use capacity earmarked for other local developments such as housing.
However, Affinity Water told MPs that some data centres were requesting as much as three million litres of water a day, equivalent to the peak demand of around 3,500 homes.
The GLA had previously warned that the proposed Hounslow development did not fully comply with the London Plan, raising concerns around transport as well as its high water and energy intensity.
As a condition of the scheme, the developer will be required to submit a strategy aimed at minimising water consumption once the site is operational.
“Where appropriate, mitigation will be secured through the planning process, while matters falling within separate statutory utility and regulatory regimes will be addressed by the relevant bodies,” a Hounslow Council spokesperson said.
The council confirmed the applicant was Brixton (Heathrow Estate) Ltd and said it did not hold information identifying a separate ultimate operator or end-user.
Under Ofgem’s proposals, large data centre developers could be required to pay a refundable commitment fee when accepting a grid connection offer, with money forfeited if developers abandon their place in the queue.
The Hounslow decision follows Ealing Council approving a 52,000 square metre data centre on the former Honey Monster factory site in Southall, close to four other data centre units approved on the Southall Industrial Estate.
Both the Ealing and Hounslow schemes still require a Stage 2 referral to the Mayor of London before proceeding, and Hounslow Council said there is currently no confirmed timeframe for that process.