Annually $41 should provide heat and hot water to New Zealand’s highest-rated energy efficient home.
Add LED lights, extra insulation and a modest size, and total electricity bills should be about $20 a month.
Owner Lawrence McIntyre hopes people will visit the house, his “little greenie”, and see they could build one themselves.
“The difference between insulating a house the way I have and the way another house is, is probably only $3000 to $4000 and the insulation value is more than double,” he said.
High quality double-glazed windows stop heat escaping, along with wool insulation and a polystyrene break to stop the concrete floor touching the ground. Sun-warmed air is directed into the walls for storage and to release heat.
The Energy Rating Authority worked out it would cost less than $50 for hot water and to heat the house to about 20C all year. The need for heating was about 85 per cent lower than an average new house, and about 97 per cent lower than an uninsulated house.
Mr McIntyre said the extra features would more than pay for themselves over their lifetime. “Really we need to move away from this [idea we should have a] pay-back period of five or seven years because the health benefits [of warm houses] … are huge.”