London plan backs greener datacentres and opens door to grey belt development

Proposals could open building on the green belt

London's future datacentre growth should prioritise "clean, green and efficient" facilities and look to grey belt land, according to the latest draft of the capital's long-term development strategy.

The draft London Plan [pdf], published by the Greater London Authority (GLA), outlines how the capital should grow over the coming decades and identifies datacentres as one of the city's industries of the future.

The document, currently undergoing public consultation, is expected to face public examination next year before being formally adopted in early 2028.

Recognising London's position as Europe's largest concentration of datacentres, the draft says digital infrastructure will play a key role in supporting AI and other data-driven industries.

However, it argues that future expansion must be compatible with the Mayor's environmental ambitions.

The plan says the benefits of continued growth will only be realised if supporting infrastructure is designed to minimise emissions, improve energy efficiency and contribute to wider climate objectives.

Grey belt sites considered where alternatives are lacking

The draft introduces a framework for deciding where new datacentres should be built, requiring planners to assess the availability of electricity and water supplies, opportunities to reuse waste heat, proximity to existing datacentre clusters and the impact on local air quality.

Authorities must also consider whether a proposed site would be better used for housing, employment or other essential infrastructure before approving digital developments.

Where no suitable sites can be identified, boroughs are encouraged to examine land in the “grey belt,” or around newly designated Broad Locations of Growth (BLGs).

BLGs are green belt areas identified as suitable for future mixed-use or industrial development.

Grey belt land, introduced into national planning policy in late 2024, covers previously developed sections of the green belt and areas that do not contribute, or do so weakly, to its traditional planning objectives.

The designation has proved controversial, with critics arguing it could make protected land more vulnerable to industrial projects.

Developers seeking to build on locations that do not meet the preferred criteria would be expected to justify their choice and demonstrate how they would reduce impacts on electricity networks, transport and surrounding communities.

The issue has already featured in high-profile planning decisions. Earlier this year, ministers approved a 147MW datacentre in Slough after determining the partly developed site should be treated as grey belt rather than protected green belt land.

Efficiency targets

Alongside planning guidance, the draft plan includes sustainability measures covering cooling systems, waste heat recovery and the operation of backup generators.

It also proposes tracking the proportion of new datacentres achieving a power usage effectiveness (PUE) rating of 1.1 as one indicator of the strategy's success.

Mayor of London Sadiq Khan has repeatedly said he only supports further investment in digital infrastructure if it meets high environmental standards.