UK Data Centre Capacity: Why the Estimates Disagree

Ask how much data centre capacity the UK has and you will get answers that differ by a factor of two or more, from sources that are each reasonable. This article puts the main published figures side by side, explains what each one measures, and sets out how to quote them without misleading anyone. Everything here comes from the cited publications; where a source is a commercial tracker or a landowner’s email, it says so.

The main figures side by side

Source	What it measures	Figure
DSIT, Estimate of data centre capacity: Great Britain 2024 (published 1 May 2025)	Maximum rated IT load of colocation data centres, by region, autumn 2024, rounded	1.6 GW for Great Britain; London 1,048 MW; South East 128 MW; Wales 154 MW; North West 52 MW; Scotland 30 MW
Buro Happold for the GLA (December 2025)	Operational capacity in Greater London, 2025	About 1 GW from 99 operational sites; 26 more in the planning pipeline (November 2025)
DC Byte, as emailed by SEGRO to Slough Borough Council (13 October 2025)	Live supply in a commercial “market”	1,478 MW for the “London” market (most of southern England and part of south Wales); 416 MW for the Slough availability zone
Oxford Economics (December 2025)	Count of operational data centres	266 operational UK data centres, 52 more announced to 2034
Baxtel (directory listing)	Listed facilities	About 600 UK facilities

Why they do not match

1. The unit differs. DSIT counts the maximum rated IT load a facility can support, in megawatts of IT power. DC Byte counts live supply in a market. A grid connection, a planning permission and a facility’s actual electricity draw are three more measures, and none of them equals installed IT capacity.

2. The facility types differ. DSIT covers colocation only and excludes enterprise and in-house data centres. The Oxford Economics count and directory listings can include more types, and directories can include small edge sites, so a count of facilities and a count of megawatts can move in opposite directions.

3. The geography differs. “London” can mean Greater London (the GLA report), the London official region (DSIT, 1,048 MW), or a commercial market that DC Byte draws across most of the south of England and part of south Wales (1,478 MW). Slough sits in the South East region in DSIT’s table, which lists only 128 MW for the whole region, while DC Byte reports 369 MW for the Slough zone alone in 2024. Both can be right, because they measure different things in different boundaries.

4. The date and rounding differ. DSIT is autumn 2024 and rounded; the GLA report is November 2025; DC Byte’s Slough figure is October 2025. Capacity in the South East has been growing by tens of megawatts a year.

5. The source’s interest differs. The Slough figures reached the council in an email from SEGRO, a landowner and developer. That does not make them wrong, but a landowner’s tracker is not an independent audit.

6. Directories rely on public sources. Manchester shows the effect: Baxtel lists 31 facilities and 32 MW, while DSIT’s estimate for the whole North West is 52 MW.

How to quote them

• Name the source and the scope in the same sentence: “DSIT estimates 1.6 GW of colocation IT power in Great Britain (autumn 2024)”.
• Give a range when you need one number for a place, and say why it is a range.
• Do not add figures from different sources together.
• Prefer the primary document (the DSIT table, the GLA report) over a summary of it, and link it.

What capacity means for solar

Capacity is not consumption. A hall that averages 5 MW of IT and cooling demand uses about 43,800 MWh a year (5 MW multiplied by 8,760 hours). At the PVGIS 5.2 modelled yield of 928 kWh per kWp at Slough, a 1 MWp roof array generates about 928 MWh, around 2% of that hall’s use (illustrative arithmetic, with a south-facing flat roof tilted 10 degrees and 14% losses). Roof solar is a margin measure at data centre scale, and the way to size it is from your own meter data rather than from a regional capacity estimate.

For the regional breakdown see the UK data centre map, and for the area guides London, Slough, Manchester, Wales and Scotland. For the cost side, see data centre solar costs. To ask a question about your own site, send an enquiry and we reply by email.