Electricity generator Powergen has confirmed that it is considering a plan to build a large wind farm in the Thames estuary near London.

It follows news that the Irish are about to build the world's largest offshore wind farm off their west coast.

With the government's long-awaited energy review expected to give a further boost to wind power, the whole industry is at a turning point.

The Thames estuary may not seem the windiest place in the British Isles, but is one of many schemes planned by the company.

Powergen, the third biggest player in alternative energy in the UK, said it was looking at this area as its possible 16th wind farm which could be a large a 500 megawatts.

All of a sudden, the cost of making a wind turbine, as pioneered by the Danish, has fallen by a factor of four.

For the first time, a kilowatt hour of electricity produced by wind is potentially as cheap as making it from gas or coal.

By 2010, 10% of Britain's energy needs are due to be supplied from renewable sources: in effect that means wind power.

But if leaks from the government are to be believed that target could be raised to as high as 20% by the year 2020.

In Powys, in mid-Wales, where wind farms supply 40% of the energy needs of the county, costs have been kept down to about 4p a unit, roughly half that of conventional electricity.

And offshore wind farms, although more expensive to build, are less environmentally intrusive, and therefore easier to get planning permission for.

Potentially, this is big growth business for no less than 178 British companies.

Across the channel, Denmark is already generating 4% of its electricity needs through wind and other alternative power sources. In Germany the figure is 8%.

In the UK, the City is sceptical that Britain can do anything like as well, and says the government will have to produce some powerful financial incentives to persuade the industry to have a go.