Hounslow's planning committee has granted permission for a new data centre on the Haslemere Heathrow Estate, a decision that sharpens the spotlight on London's growing role as the nation's data hub and the strain such developments place on local infrastructure.
The proposals, debated at length by councillors, reveal how London now accounts for the lion's share of the UK's digital backbone: as of last November there were 99 operational data centre sites in London and a further 26 in the planning pipeline, according to the Greater London Authority (GLA).
Energy, water and planning tensions
Government guidance frames data centres as critical infrastructure, saying they "underpin almost all economic activity and innovation". But regulators and local authorities have repeatedly warned about their demand on the electricity grid and local utilities.
"underpin almost all economic activity and innovation"
Ofgem has previously identified data centres as a major driver of electricity demand across Great Britain. For the Haslemere scheme, planning officers told Hounslow councillors the site would import power from the National Energy System Operator using the Laleham Grid Supply Point, a connection that routes capacity outside the borough's boundaries. Officers also stated the centre would not draw on electrical capacity reserved for other local developments such as housing.
However, the application did not provide clear detail on the scheme's impact on local water supplies — a sensitive issue for communities served by Affinity Water. In May the company told MPs that some data centres were requesting as much as 3 million litres of water a day, the equivalent of the peak demand of around 3,500 homes.
GLA flagged shortcomings
The GLA's initial Stage 1 report raised concerns that the Haslemere proposal did not fully comply with the London Plan. It cited worries over transport, and the development's high water and energy intensity. Under the terms of approval, the developer is required to submit a strategy to minimise operational water consumption before full operation.
Local campaigners and residents who have watched a string of data centre applications come before Hounslow council will want to see rigorous monitoring and enforceable conditions attached to any permission. The planning papers show the council sought assurances that the development would not cannibalise energy capacity intended for housing or other community infrastructure.
- Operational sites in London: 99
- Sites in planning pipeline: 26
- Share of UK capacity in London: c. 80%
- Reported peak water requests by some data centres: up to 3 million litres/day
| Metric | Figure |
|---|---|
| Operational London sites | 99 |
| Sites in planning pipeline | 26 |
| Estimated share of UK capacity in London | ~80% |
| Reported water request by some centres | 3,000,000 litres/day |
The decision to approve the Haslemere development reflects a tension at the heart of modern urban planning: supporting digital infrastructure that fuels economic activity while protecting local services and meeting policy tests on sustainability and transport.
Hounslow councillors were told the connection to the Laleham Grid Supply Point avoids using constrained local electrical capacity, but the absence of a robust water strategy in the application prompted specific conditions. Officers have required a comprehensive plan to reduce operational water consumption as part of the discharge of planning obligations.
With around half a million people visiting Oxford Street each day and London accounting for roughly four-fifths of UK data centre capacity, the capital's competing demands — for leisure, housing and digital infrastructure — are becoming sharper. The Haslemere approval will add to the urgency of strategic decisions on how and where to permit energy- and water-intensive developments.
For residents and local businesses the practical questions remain: how will local networks be protected, who will pay for upgrades, and will promised mitigation measures be enforced? The developer must now deliver the required strategies and evidence that operational impacts on water consumption are minimised before the centre becomes operational.
As London continues to host more of the UK's digital infrastructure, local authorities, the GLA and utility regulators will face sustained pressure to balance regional economic priorities with environmental limits and the needs of communities.
