UK Data Centre Boom Hits a Cabling Bottleneck as Pipeline Passes 14GW

The UK’s data centre build-out is running into a bottleneck that gets far less attention than power or GPUs: cabling. In a survey of senior data centre decision-makers by infrastructure specialist Onnec, 77% of UK operators said they face critical bottlenecks sourcing the cabling needed for AI workloads. Another 72% said the AI rush is creating cabling problems that could take years to fix, TechRadar reported.

Built, then immediately outdated

The survey found that 83% of operators say AI requirements have moved on so much by the time their hardware is running that upgrades are needed almost immediately. In addition, 37% report latency or bottleneck problems with AI training, and 33% can’t scale without significant cabling work. And 44% said poor upfront cabling planning had already caused delays or extra costs.

“Everyone is focused on securing power and GPUs for AI, but the network connecting that hardware together is too often finalised only after those decisions have already been made,” said Matt Salter, global head of data centres at Onnec. “You can have the power and GPUs in place, but they still need to communicate. If the network cannot support that traffic, the AI environment will not perform as expected.” His advice is to make cabling part of the design before layouts and pathways are fixed. “Otherwise, today’s AI build-out will leave teams carrying out expensive work inside live facilities much sooner than expected.”

A pipeline that keeps growing

The pressure comes from the size of the pipeline. An analysis of Barbour ABI planning data by Computer Weekly counts 173 committed projects, meaning schemes that have entered planning but aren’t finished, totaling 14.6GW. In March there were 114 projects and about 10GW. Another 4.4GW sits in pre-planning, bringing the total to close to 19GW headed for the UK grid.

London and the M4 corridor still dominate by volume, with 82 projects and 5.2GW. The biggest campuses, though, are going north. The average North East scheme is 228MW, against 77MW in London and the M4 corridor. Scotland’s committed pipeline more than tripled in six months, from 0.9GW to 2.4GW. Computer Weekly said the pattern reflects large brownfield sites such as former power stations with access to high-capacity transmission, and a growing pipeline “competing for a finite supply of grid connections and power.”

For operators and their customers, power is still the hardest constraint. But the survey suggests that a network designed after the power and GPUs are already set can limit how well a facility performs, and can mean expensive retrofits soon after it opens.