The cost of offshore wind power in the North Sea is 30% lower than that of new nuclear, writes Kieran Cooke – helped along by low oil and steel prices, reduced maintenance and mass production. By 2030 the sector is expected to supply 7% of Europe's electricity. Output from the Dogger Bank project will be 1.2 GW (gigawatts) – enough to power more than a million homes. Next year, a 150-turbine wind farm off the coast of the Netherlands is due to start operating, and other schemes along the Dutch coast are in the works. Denmark, Sweden and Portugal are major investors in offshore wind, and China has ambitious plans for the sector. Wind farms – both onshore and offshore – are a key ingredient in renewable energy policy, and an important element in the battle against climate change. WindEurope, an offshore wind industry group, says that at the present rate of installations it's likely Europe will be producing about 7% of its electricity from offshore wind by 2030.Offshore wind developers benefit from falling costsBy some calculations, all this building work would seem to make little economic sense. Fossil fuel prices are low on the world market, and constructing offshore wind farms several kilometres out at sea, in often treacherous conditions, has traditionally been an expensive business.