Hydropower has an advantage over wind and solar energy in that while seasonal fluctuations in rainfall will raise or lower the amount of power that a mill can generate, it will rarely cease altogether. More power will be generated in winter, when demand is higher (the reverse is true of solar energy).

Finding an old water mill to recommission generally means scouring the listings of rural estate agents and auction houses. There are also bodies, such as English Heritage, the Scottish Civic Trust and the Ulster Architectural Heritage Society, that maintain lists of buildings at risk, sometimes including mills for sale.

Jon Dakin, at the Winchester office of John D Wood, is currently selling one old mill, converted in the 1920s. “They are popular — mostly with people who have moved out of London, maybe retired. Families with young children are a bit wary because the mill streams are fairly energetic water flows.

“When you show people around, they always say, ‘Gosh, wouldn’t it be great to get it going again!’ So, yes, it can add to the value of the property.”

Like Shingler, Sonia Newton, who owns Sowton Mill (actually two mills, side by side) in Dunsford, Devon, inherited her property. But hers has been generating electricity for longer than Shingler’s. The old flour mill dates from 1581, with the new mill built in 1810. Newton’s forward-thinking father bought them in 1945, drawn by their potential for generating electricity. He converted the old mill into a home before focusing on the new mill.

“He bought an old war generator and harnessed it to the water wheel,” says Newton, looking at the old wheel — long covered in a thin coating of rust since being superseded by a modern turbine. “After he died, I became more and more interested in it, and my mother and I put our capital together and installed the present system in 1986, costing about £40,000, which was a fortune then. But running costs are very low. I’m 75, and I still do most of the maintenance myself — replacing the odd bearing and so on. Yes, we’ve had the odd upset because in the early years we didn’t know so well what we were doing — like when the weir gates froze one winter and we had to whack them open with sledgehammers; that wasn’t so much fun. But it has been worth it.”

Her main motivation was a desire to see the old mill working again. “As much as anything else, we did it because the water was there and it seemed a shame not to use it,” she says. “It was only later that we realised we could make money out of it. Over the past 20 years, we have got about £5,000-£6,000 a year out of it, which pays for the odd drink on the turbine, and it should last for many decades to come. I think anybody who can do this, should. Definitely.”

• British Hydropower Association, 01202 886 622, www.british-hydro.co.uk; Clear Skies, 08702 430 930, www.clear-skies.org; Energy Saving Trust, 020 7222 0101, www.est.org.uk; English Heritage, www.english-heritage.org.uk; Gants Mill, 01749 812 393, www.gantsmill.co.uk

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