The United Kingdom's grid-connection register holds 50 GW of data centre demand from roughly 140 data centres, against a national peak electricity use of 45 GW recorded on 11 February 2026.1 Total contracted offers in the UK demand queue reached 125 GW by mid-2025, up from 41 GW in November 2024, a tripling in seven months.
The register is maintained by the National Energy System Operator (NESO), the body that took over GB grid operation from National Grid ESO in October 2024 under the Energy Act 2023. It tracks every signed connection offer, distinguishing data centres from generation, electrolysers, and other large industrial loads. The 45 GW peak figure comes from NESO's own demand monitoring on a cold February evening when the British electricity system was running near full deliverable capacity.
NESO's own February register puts the data centre sub-queue alone above the entire country's recorded peak demand, and the wider queue at 125 GW is roughly three times peak. Most of those connection offers will not be built; queue-clog is a known feature of the GB system, with operators submitting speculative requests to hold optionality. Ofgem's "Curate, Plan, Connect" reform workstreams, announced in February 2026, are designed precisely to filter speculation from intent and re-rank the queue by readiness. The reform is the single largest UK grid-connection policy intervention since privatisation.
The disclosure is the event because it gives the OpenAI Cobalt Park pause its quantitative context. When a US operator describes the UK regulatory environment as "unfavourable", this register is what they mean. The 125 GW queue cannot connect on the timescales hyperscalers need; the 80% that NESO and Ofgem will likely strike off as speculative still leaves a real pipeline that exceeds available transmission headroom for the rest of the decade. Whether Ofgem publishes its AI-demand consultation response this quarter is the next decision the market is watching.
