The government has said households that install solar panels in the future will be expected to give away unused clean power for free to energy firms earning multimillion-pound profits, provoking outrage from green campaigners.

The mayor of London, big energy firms and environmentalists had urged ministers not to end the “export tariff” for solar panels under the feed-in tariff scheme, which is closing next year.

But officials confirmed that anyone who adds solar from April 2019 will not be paid for any excess power they export to the grid.

Solar panels on sloped roof of house on overcast day

Climate change charity 10:10 said the decision was bizarre and urged a rethink to avoid pushing solar “off a cliff” next year.

“It’s hard to fathom the government’s logic here. Solar has been a huge success story, seeing 1m homes and 1,000 schools taking clean energy and climate action into their own hands,” said Neil Jones, a campaigner at the group.

Green peer Jenny Jones said the step was a “very bad call”, while people took to social media to brand it “absolutely outrageous” and “shocking”.

The change will not affect the 800,000-plus homes that have already fitted solar panels since the feed-in tariff scheme launched in 2010.

The Department for Business, Energy and Industrial Strategy said it was ending the export tariff, which provides a guaranteed price for all unused solar electricity, to minimise costs to all consumers. The policy did not align with its industrial strategy, it added.

Read more: Future Build