The Conservatives’ new leader hopes that the fee of more than £10,000 for Alex Michaelis to provide green heating, lighting, insulation and fuel systems will be recouped on lower bills.

Mr Michaelis, 40, will redesign the Camerons’ new £1 million house in Notting Hill, West London, when they move in next month. Mr Cameron is moving because he wants more room for his disabled four-year-old son and the baby his wife Samantha is expecting in February.

The architect, who has attracted national attention for the design of his own underground home in nearby Ladbroke Grove, said that Mr Cameron was one of a growing number of clients who wanted an eco-friendly makeover.

The Tory leader, who regularly cycles to the Commons, is also acutely aware that environmental issues strike a chord with the younger voters he must attract to make his party electable again. He has already set up a commission to review party policy jointly chaired by the environmentalist Zac Goldsmith.

Mr Michaelis, a partner in Michaelis Boyd Associates, said: “The starting point will be to insulate the existing house, a two-storey Victorian terrace. The basement will also be made bigger for David’s disabled son and will have light wells front and back.

“Thermal solar panels on the roof will heat water and photovoltaic solar panels will convert light into electricity, which you can put back into the grid or do a deal with energy suppliers.”

But the pièce de résistance will be the wind turbine — provided that Mr Cameron can get planning permission.

Mr Michaelis said: “They are slightly bigger than a satellite dish and akin to a spinning aerial. They are 1.75m in diameter and make very little noise. Most people don’t look at roof- scapes anyway.”

He said that his design would incorporate “water harvesting” — a tub to catch rainwater — as well as “recycling grey water” — filtering bath and shower water for use in the washing machine.

Windows will be brush-sealed at a cost of £30 to £40 each and some may be fitted with “K” glass, which cuts heat loss. The solar panels cost between £500 and £1,000, while the photovoltaic panels cost up to £3,000. An air circulation system costing £1,500 will take warm air out of bathrooms and use it to heat colder rooms.

Mr Michaelis said that he was charging Mr Cameron the usual rates for his work with “no special deal” for his celebrity client. “In the last four or five years a lot more people have become interested in eco work and a lot of clients can afford to have it done,” he said.

Mr Cameron said: “Politics is about more than just elections. We are all in this together and each of us can do something to make a difference.”

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