Rooftop solar can only meet a small share of a data centre's electricity, often around 1%, because the load is so large and constant. It is still worth doing, because every kWh is used on site, but the bigger opportunities are ground-mounted solar on nearby land, private-wire supply, batteries and off-site Power Purchase Agreements.
The scale problem, in numbers
Take an illustrative facility with a 20 MW IT load and a power usage effectiveness (PUE) of 1.3. It draws about 26 MW, around the clock, which is roughly 228,000 MWh a year.
A 15,000 m² roof at the calculator's assumptions takes about 2.4 MWp of panels. At UK average sunshine, that generates around 2,100 MWh a year: about 1% of the site's demand.
Where solar adds value
- Rooftops, offices and ancillary buildings. Every kWh is used, and the system pays back well.
- Car parks. Canopies add generation and shelter, and can power staff EV charging.
- Land on or next to the site. A ground-mounted array supplying the data centre directly through a private wire can be tens of times larger than the roof.
- Batteries. Storage can manage peaks, support grid connection limits and work alongside backup systems, though backup design needs specialist input.
- Off-site PPAs. For most of the demand, operators sign long-term contracts with solar or wind farms elsewhere on the grid to match their consumption and report lower Scope 2 emissions.
Grid and planning context
Grid capacity is one of the biggest constraints on new data centres in the UK. On-site generation and storage do not replace a grid connection, but they can reduce what the site draws at peak and strengthen the case with the network operator. Data centres are now designated as Critical National Infrastructure, so any on-site energy project must fit the site's security, access and resilience requirements from the start.
Rooftop solar on the buildings is normally permitted development in England. Larger ground-mounted arrays need planning permission. See planning and grid connection.
Getting started
- Model the roofs and car parks in the calculator, with "solar used on site" set to 100%.
- Identify any land on or next to the site that could host a larger array.
- Bring energy, security and facilities teams together early, because access and resilience requirements shape the design.
Common questions
Can solar power a data centre?
Not on its own. Rooftop solar typically covers around 1% of a large data centre's demand. Larger nearby arrays, batteries and off-site PPAs are needed to make a significant difference.
Is rooftop solar still worth it on a data centre?
Usually, yes. The site uses every kWh the panels produce at its full unit price, so returns are strong, even though the share of total demand is small.
What is a private wire?
A direct cable from a generator, such as a solar array on neighbouring land, to the site that uses the power, rather than sending it through the public grid.