What is a data centre?

A data centre is a building designed to house computers, usually thousands of servers, and keep them powered, cooled, connected and secure around the clock. Almost everything you do online runs in one.

What's inside

From the outside most data centres look like large, windowless warehouses. Inside, servers sit in metal racks arranged in rows across big rooms called data halls. Each rack draws a lot of electricity and gives off a lot of heat, so much of the building exists to deal with those two things.

• Power: a grid connection, transformers and switchgear, plus UPS systems (large banks of batteries) that take over instantly if the grid fails, and diesel or gas generators that start within seconds to carry the load for longer.
• Cooling: chillers, air handling units and, increasingly, liquid cooling piped close to the chips, because AI hardware runs far hotter than ordinary servers.
• Connectivity: fibre from several network providers, so the site stays online if one route is cut.
• Security: fences, controlled entry, CCTV and staff on site day and night.

The main types

Colocation sites rent space, power and cooling to many customers who bring their own equipment. Hyperscale sites are built by or for the large cloud companies and can run to hundreds of megawatts. Enterprise data centres belong to a single organisation, such as a bank, for its own use. Size is usually described in megawatts (MW) of IT power rather than floor area.

Why so many are being built in the UK

Demand for cloud computing has grown for years, and AI has sped it up sharply: training and running AI models takes far more power per rack than traditional workloads. The government has also set up AI Growth Zones to speed up grid connections and planning for large sites. The limits now are mostly power, land and skilled people.

Who works in a data centre

A finished site runs with a relatively small team: technicians who handle the IT hardware, critical facilities engineers and electricians who keep power and cooling running, plus security and operations managers. Building one takes far more people, often several hundred at peak, across construction and commissioning roles.

Where they are

We track 49 UK sites, 18 of them still being planned or built. West London and Slough have the densest cluster, because that is where the fibre and power have been for decades. See them all on the map.