ore to offer than a conventional house. He hopes to build the real thing and sell the concept to home buyers.

"My main reason for wanting to do this is because pyramid homes are so energy efficient," he said. "They are much cheaper to build and the maintenance costs are a lot lower."

This is not the first time the military veteran, who worked on nuclear submarines, has looked at the advantages of a pyramid home.

"About 24 years ago, I actually built a pyramid home in Arkansas, which I lived in for a couple of years," said the father of five. "It was very, very energy efficient. I remember when it snowed, and there was about a foot of snow all over the house. The house was so warm and out of the three months of winter I only had to heat it for about a month. And in the summer it stayed very cool."

The Sierra Vista resident is no stranger to the world of inventing and engineering. Last year, Robertson came up with an idea called the Solar Tree, which he described as "an innovative, new solar-powered home-improvement product that will help lower utility bills."

His invention, which looked like a tree, was designed to use solar power to heat water, a swimming pool, or to power lights, and it received a lot of interest.

However, after later discovering several other similar products already on the market, Robertson decided to concentrate his efforts on his pyramid house.

"It's still being developed. It's not at the point where I want it yet," he said. "There's a lot of things I want to change, following my previous experience of living in a pyramid house."

Robertson says the shape of a pyramid home naturally lends itself to saving energy.

He points to the "pyramid power" theory, where some believe the exact dimensions of a pyramid creates an electrical energy.

"It's just something about the shape," Robertson said.

"When I took the temperature in my pyramid house at the bottom of the building, it was the exact same temperature as it was at the top. I would have expected the top of the house to be warmer, because hot air rises, but it wasn't. It was totally amazing and meant my maintenance costs were low."

Robertson's design, which he calls the "Stepping Stone House," has solar panels on one exterior wall to power the home.

Next to it is a two-car garage, and on top of that, leading from the master bedroom of the two-story building, is a greenhouse.

"Although this house looks different, it won't stick out like a sore thumb," he said. "I think if you placed a house like this among other homes, it wouldn't throw things off."

Robertson's plan is to find a piece of land to build his 2,000-square-foot pyramid home, using conventional materials. He estimates it will cost around $75,000 to construct.

He then hopes to eventually set up a manufacturing business - he has already registered his company as Pyramid Industries - where the homes will be built in pieces, delivered to the customer and built in just a few days.

"I think there will b

e a lot of people interested in a project like this," he said.