The first green energy subsidy auction to be held for two years is expected to pave the way for an offshore wind boom, as the costs of building renewable farms out at sea tumble faster than experts predicted.

The Government has set a £730m budget for three auctions for emerging renewable technologies by 2019, and it has ruled out pouring any more funds into onshore wind and solar energy.

The first of the three, a £290m auction, will kick off this week, and is expected to show that the decline in costs is about a decade ahead of schedule.

Ben Warren, a partner at EY, said the “huge interest” in the auction should cut the cost of offshore wind by a quarter from previous winning bids.