The UK is in the midst of a green energy transformation, with more than 40% of its electricity coming from wind power as of December. But wind can be unpredictable and the grid can’t always handle the power wind turbines generate on blustery days — and so to protect the grid, operators sometimes pay wind farms to power off. 

After Bloomberg’s investigations team received a tip about troubling inaccuracies in the data used to calculate these payments, our reporters went looking for answers. And they found a big problem lurking in the UK’s renewable energy market: some wind farm operators were routinely overestimating their production forecasts, and traders and market experts say that, in effect, they’re getting paid to stop producing power that they wouldn’t have produced anyway. 

According to Gavin Finch and Todd Gillespie, the reporters who led this investigation, the price tag for consumers is in the millions of pounds. And with the UK aiming to triple the number of wind turbines in the country by the end of the decade, those costs could increase.