The largest hydroelectric facility of its kind in southern England will provide a third of the power at the royal residence - the largest occupied castle in the world - it was announced this week.
Power will come from the £1 million, 200 kilowatt Romney Weir Hydro Scheme, to be located on the Thames next to Romney Island between Windsor and Eton, in Berkshire.
It will consist of four turbines in two of 10 bays that will make up a weir. The turbines will be underwater to lessen their visual impact.
Construction is due to begin next year. The government has a target of producing 10 per cent of the UK's electricity requirements from renewable sources by 2010 and 15 per cent by 2015.