I reckon there are 75,000 people living in nearly 25,000 off-grid homes in the UK. These are homes not connected to mains gas and electricity, water and sewage or even the phone lines that bind the rest of us into a system that wastes energy transporting it around the country, and loses up to 30% of water through leaks.

To get some idea of how many are living this way, I travelled round the UK for most of last year researching a book, How To Live Off-Grid. I met some of the thousands of normal families living this way, in everything from brick houses to yurts.

Roy and June Fountain, in Kirkby Malzeard, north Yorkshire, live comfortably and conventionally in a normal looking house that gets its water from a borehole and its electricity from a wind turbine. Roy Fountain is a retired farmer, not an environmentalist, who bought a derelict cottage and moved his family into it. He battled for years for planning permission to live this way, and succeeded only by starting a sheep-milking business, which was not his original intention, but it was the only way he could persuade the local council that he had a legitimate reason for living off-grid.

He is in a minority among the off-gridders. Most of the ingenious, self-reliant people who live this way have built their own wooden cabins in fields or parked their caravans behind hedgerows; driven camper vans or converted lorries deep into woodlands; live aboard boats, many of them moored on inner-city canals; or, in the most extreme cases, inhabit tree houses and benders erected in woods and fields.

Benders are shelters made from saplings bent into a lattice frame, supporting a canvas roof and walls. There were more than 10,000 recorded in the 1815 census, and now they are making something of a comeback. The rest of us can learn from these ecological footsoldiers about how to live low-energy, low-impact, low-carbon lives.

Perhaps the nation's off-grid housing stock can be classed as an investment in a carbon-free future. Every off-gridder automatically reduces their energy and water consumption by up to 90% compared with a typical household. They live each day aware of the sun and the wind - dependent on the elements, and so closer to them.

The figure of 75,000 is only those living off-grid all year round. It does not include part-time off-gridders - the winter renters who go out in their vans or take to their yurts and caravans. This triples the winter numbers.

But why does any of this matter, other than to the people who live this way? Because off-grid living could help the government meet two of its key aims: more affordable homes, and lower domestic carbon consumption.

Despite all the government's talk of affordable housing and eco-towns, it is well nigh impossible to get planning permission anywhere that is truly affordable. The prime minister's pledge to build five eco-towns is all very well, but to be truly sustainable, shouldn't they start as eco-villages and grow organically? They need to be populated by people who have the desire and knowhow to live sustainably. Where is Gordon Brown planning to find these paragons other than from among the current off-grid population?

On this crowded island, it is the building land that makes homes unaffordable, not the house itself. Anyone can buy a few acres of woodland or meadow for perhaps £20,000 - compared with up to £150,000 for a conventional building plot - and build a low-impact wooden house with solar panels and a wind turbine for another £40,000, including the obligatory composting loo and rainwater harvesting kit. But getting residential planning permission to live there is always a battle. What could be an eco-solution to Britain's housing shortage is being stifled by intolerant regulations.

Right now, there is a window of opportunity for a flood of off-grid housing, low-density eco-dwellings hidden in woods or behind hedges, a few houses here and there. But it would require a complete break with the planning laws as we have known them for the last 60 years. Consultation is still in progress, until August 17, on the recently published planning white paper, Planning for a Sustainable Future. This is the proposed new regime that will push through large national infrastructure projects. Its reforming scope could be expanded, allowing a large number of exceedingly small developments.

I would like to see a new category of off-grid planning permission that would allow low-density, low-impact off-grid homes to be built in the open countryside or even the green belt, as well as cities, on the strict condition that these homes remain off-grid for ever. Unlike the current agriculture-tied planning permission, which can be lifted as more and more agricultural workers leave the land, it would be essential that an off-grid home could never be transferred to grid-connected. Not only could this new category make it possible to create an extra 20,000 homes a year, on the 90% of the country not currently developed, it would also be a major contribution to reducing our carbon footprint.

One group is in the process of testing the appetite of planners for recognising off-grid living. The Landmatters collective in Devon is battling South Hams council to remain living off the land near the heart-achingly beautiful village of Allaleigh. One day there was just a beautiful hilltop pasture. The next morning there were a dozen benders in the field - and the Battle of the Benders had begun. A public inquiry has just been held, the outcome of which could set the terms for future attempts to live off-grid in the countryside.

A slight tweak to the planning system would allow 30,000 new homes a year in open countryside without spoiling anyone's view - just breathing life back into dying village communities and launching a social experiment that could be a major part of our solution to global warming. The main obstacle, apart from national planning policy, is from neighbours who paid a fortune for their land and do not see why someone else should get land in the area for £5,000 an acre. Huge numbers of affordable flats are being built in city centres, but if we accept that the countryside also needs affordable housing, then where else is it going to come from?

· Nick Rosen is a TV producer and campaigner. His book How To Live Off-Grid is published by Doubleday (£12.99). To order a copy for £11.99 with free UK p&p go to theguardian.com/bookshop or call 0870 836 0875. For more information on living off-grid go to off-grid.net