Over 3m homes will receive renewable energy from E.ON UK at no extra cost in its biggest green energy switch to date as a response to the climate crisis.

E.ON is one of the UK’s largest renewable energy generators and plans to draw from its own windfarms, biomass plants and solar projects to power the switch.

The company also needs to top up its portfolio by buying renewable “guarantee certificates” to guarantee that a set amount of electricity has been generated from a specific project.

Michael Lewis, the chief executive of E.ON UK, said the supplier has secured enough renewable energy to confidently meet the demand of its customers.

He said the switch is “an investment in our customer relationship”, which would also help “drive the market” for clean energy.

E.ON is the first of the U.K.’s “Big Six” utilities to do supply its customers with 100% renewable energy and could help EON differentiate itself in an increasingly competitive market and especially at a time when people are becoming more aware of the fight against the climate crisis.

“Climate change is the defining issue of our era, and one that energy customers are increasingly concerned about,” said Michael Lewis. “This is a change at a scale never seen before in Britain.”