Water and electric power plants do not mix well naturally, unless you add some wind, as water tends to corrode and short out circuits.

So what’s happening in the renewable energy industry, where developers are putting jumbo-jet sized wind turbines into stormy seas, is at the very least an engineering miracle.

Bloomberg newsagency reports what might be even more miraculous to sceptics like those populating United States President Donald Trump’s administration is that these multi-billion-dollar mega projects make increasing economic sense, even compared to new coal and nuclear power.

“If you have a sufficiently large site with the right wind speeds, then I do believe you can build offshore wind at least at the same price as new build coal in many places around the world including the US,” said Henrik Poulsen, chief executive officer of Dong Energy.

The Danish utility has pioneered the technology and has become the world’s biggest installer of wind turbines at sea.

Across Europe, the price of building an offshore wind farm has fallen 46 per cent in the last five years, 22 per cent last year alone.

Erecting turbines in the seabed now costs an average US$126 for each megawatt-hour of capacity, according to Bloomberg New Energy Finance (BNEF).

That’s below the US$155 a megawatt-hour price for new nuclear developments in Europe and closing in on the US$88 price tag on new coal plants, the London-based researcher estimates.

As nuclear power costs spiral, prompting a US$6.3 billion write-down at reactor maker Toshiba Corporation and delays at Electricite de France’s plant in Flamanville, the investment needed to build offshore wind capacity is plummeting.

In Denmark, where the government shoulders much of the development risk, Vattenfall last year agreed to supply power from turbines in the North Sea at €60 a megawatt-hour in 2020.

Dutch and German auctions due this year provide “ample opportunity” to beat that record low price, says Gunnar Groebler, the utility’s head of wind.

The industry even is taking hold in the US, which for years shunned the technology as too costly for a place that historically enjoys lower power prices than Europe.

A bidding war erupted at a federal auction in December for rights to develop wind farms off the coast of Long Island.

Rhode Island has commissioned one plant, and developers are also considering work in Maryland, New Jersey and North Carolina.

Although President Trump said offshore wind was “monstrous” when it came into conflict with his golf course in Scotland, the US government’s official goal for now is to install 86 gigawatts (GW) of turbines at sea by 2050.

That’s six times the 14GW of capacity now in place worldwide, according to the Global Wind Energy Council.

Oil majors such as Royal Dutch Shell and Statoil are among companies that won contracts to build offshore wind projects last year.

All told, a record US$29.9 billion was invested in offshore wind in 2016, up 40 per cent from the year before, according to BNEF.

It expects investment to grow to US$115 billion by 2020.

What’s driving installations is an expected 26 per cent drop in the costs, making offshore wind increasingly competitive with land-based turbines and solar and nuclear power, even without subsidy.

In years past, grid managers were reluctant to rely on fickle winds for power that flows only about 45 per cent of the year.

However, battery costs have fallen 40 per cent since 2014, making them a realistic way to help balance fluctuating flows of renewable energy to the grid.

Bloomberg reports offshore wind projects coming online today are already delivering power at almost half the price of those finished in 2012 thanks to larger turbines and greater competition.

Europe’s lingering low-interest environment may add downward pressure on bids in Germany’s offshore auctions, EON Chief Executive Officer Dr Johannes Teyssen said.

The utility will join bidders as it seeks to add as much as €1.5 billion a year to its clean energy portfolio.

The United Kingdom remains one of the hottest markets owing to the need to replace ageing power plants.

Bids may reach as little as €80 a megawatt-hour in the next auction due to start in April, she said.

“In this auction it is possible that the price achieved could be below 90 pounds,” said Keith Anderson, chief corporate officer of Scottish Power, a unit of Spain’s Iberdrola.