Work to build what has been described as the biggest roof-mounted solar panel array in the UK has started at a Marks and Spencer distribution centre.
More than 24,000 panels will be spread across the Castle Donington building's roof - which is the same size as 11 football pitches.
M&S said the panels would produce almost enough electricity to make the building "self sufficient" in the day.
The Leicestershire site handles all of the products the firm sells online.
When it was built in 2013 it was the UK's largest dedicated e-commerce warehouse.
Adam Elman, head of global delivery for M&S's eco and ethical plan, said 24,272 panels would cover the 900,000 sq ft (83,613 sq metre) roof.
"Importantly as well as reducing our carbon emissions, it will make our site almost self sufficient during the day," he said.
"It will produce 5,000 MWh of electricity a year that's equivalent to the power of around 1,190 homes."
He said the building already had one of Europe's largest solar walls.
The solar array should be complete next year.