Life off the grid: one pioneering family's experience

Who lives there: Writer Murray Grimwood (53) and teacher Jennie Upton (45), their cat and dog, and on and off, their two teenaged sons.

Where: 25 minutes north of Dunedin, off State Highway 1.

Claim to sustainability: Off-grid home, carbon-sink forest, bath vegetable garden.

• Power self-sufficiency possible

If you go looking for a gadget or even an appliance in the Grimwood-Upton household you could be looking for a while.

Gadgets and appliances use electricity and as Murray and Jennie's home north of Dunedin is not hooked up to the national grid, they keep them to a minimum.

The power to run their household comes from a simple solar panel and a wood stove, with backup from a petrol generator when needed.

They do have cellphones, laptops, a stereo, a washing machine and a television.

However, the stereo is from a car (uses less voltage) and the television (which is only turned on to watch the odd movie) and washing machine run off a generator.

"We've not made any real sacrifice to go off-grid," they said.

But why, many of us would ask?

It came down to two things.

They owned a forestry block 25min north of Dunedin, buying it in 1994 for its carbon-sink forest, and their home in Waitati, which was part crib, was restricting the growing family.

With those issues in mind, along with Murray's desire to have a go and see what he could build on a $50,000 budget, the family decided to build on the block four years ago.

"We wanted to see what we could do on a tight budget."

So the open-plan, two-level home was built using "super-insulating" chiller panels, usually used in cool stores, with the few inside walls made of single sheets of plywood, and the north face of the house mainly windows.

The windows for the large conservatory, which traps the sun and feeds the heat back into the house through wooden air vents, came from the old Ansett terminal at Dunedin airport.

Various ingenious uses of air circulation had been used to keep the house warm, he said. "It's super-efficient."

They used offcuts of wood people did not want to create a large kitchen table, stairs and shelving.

Lighting is provided by home-made LED lights, which use barely any electricity, and cooking is done on a gas hob and wood stove.