UK Renewable energy production is still subsidised by Contracts For Difference. What happens is the government says OK, for this power we're willing to pay extra. Bid for how much you want. Some offshore wind farm builder might say OK, pay us £65 per MWh in 2020. No better offers in that category (low risk zero carbon power)? OK. Every MWh you generate in 2020 the electricity grid pays whatever they'd pay for gas or coal or anything else, then, the difference between that and £65 per MWh is from the government. Maybe the grid pays £20 right now, subsidy is £45. But, maybe the wants every amp they're paying £95 right now, the government gets £30 back from the wind farm.

CFDs make investors comfortable. Wind farms are expensive, what if we take out a loan to build this expensive wind farm and only get £15 per MWh we'd go bankrupt. If the government promises £65 we're profitable so long as we build that wind farm. CFD bidding also drives down costs, if your rival will take £35 the government may not accept your bid.