David Cameron's green idea has been blown away

North Kensington isn't one of London's windiest spots. In fact it's in a windless dip, at the foot of Notting Hill. Which is one reason why David Cameron's plans to install a wind turbine on his home struck those of us who live near him as rather silly.

The other reason was that we — and he — live in a conservation area. A leafy grid of red-brick Edwardian terraces, additions, extensions, satellite dishes, even weather vanes are outlawed if they are visible from the street.

We agreed the turbine was a political gimmick which would neither save the planet nor save Dave much on his energy bills. "Let's hope he doesn't get permission just because of who he is," we muttered. And we vowed to dragoon Kensington and Chelsea planners into rejecting this proposed blot on our cherished roof-scape.

But in this eco-minded part of west London, being green is the new religion. Few wanted to voice such doubts publicly. Besides, it's not nice to complain about your neighbours, especially when, as one resident put it, "he's added at least £20,000 to the value of our houses by moving here". (That was pre-credit crunch.)

Mr Cameron got his planning permission and the wind turbine went up, extending an unsightly three metres above his roof. A few days later it came back down: the planners had noticed it was in the wrong spot. And yes, we did all snigger. Permission was re-applied for last February but there's been neither sight nor sound of the turbine since.

Now we know why. Our scepticism was well-placed. It's official: according to a recent survey, domestic wind turbines don't generate enough energy to be viable. Some can't even power their own electronics.

A few days ago B&Q announced that it would stop selling them. Even Dave has admitted it was all a terrible mistake. His D400 Stealthgen was reported to have cost around £3,000: it was estimated it would take 40 to 70 years to pay its way. B&Q's models were cheaper but you would still need lots of time, not to mention cash, to make one worthwhile. Unless you live on top of a hill.

"If he really wanted to be green he could have moved to Freston Road [North Kensington]," one of Mr Cameron's neighbours suggested helpfully this week. "It's very windy there." Indeed the wind does howl, between the walkways of the post-war tower blocks. And they're not in a conservation area.