The domestic hot water stored in this tank is heated almost exclusively by the sun.

Few people have the leisure, money and know-how to build a house largely as an experiment. But semi-retired house designer Frank DiMauro says that’s exactly what he did on a piece of land near Tiverton Four Corners.

After a career that included designing large luxury homes, DiMauro said he wanted to try his hand at building a house that would be very small, very green and very cheap.

He also wanted to incorporate solar energy into the heating and electrical systems.

The result is a 1,008-square foot, two-story, single-family house, a structure that DiMauro calls his “eco-cottage.”

The house is at the corner of East Road and Eight Rod Way in Tiverton, across the street from an entrance to the Weetamoe Woods recreation area and next door to a Tiverton fire substation.

DiMauro says solar energy should be a part of “mainstream” residential building today, but it isn’t, perhaps because no one can claim to own the sun, or charge money for sunlight.

But he says solar systems are simple and relatively inexpensive to install and operate.

He is renting out the cottage by the week or month to give people a chance to become familiar with solar, and he has given tours of the cottage to students working on science projects. He said he also invites interested builders, plumbers and electricians to come by for a look.

The cottage roof has thermal solar panels that provide hot water, and photovoltaic panels that generate electricity.

DiMauro said the house’s solar hot-water system was installed for $4,000, making the cost about the same as a conventional system. But the house’s National Grid electric bill for June 10 to July 10 was $0.00.

“Instead of $12,000, it cost $4,000, so a [solar energy] company could sell [systems] for $6,000 or $7,000 and still make money,” DiMauro said.

“With the present tax credits, the system will pay for itself in two or three years and give you 80 percent of your domestic hot water needs free for the next 15 to 20 years.”

The solar-heated water is also used to partially heat the home, through radiant heat tubes embedded under the first-floor; DiMauro estimated it provides about 30 percent of the house’s heat.

Even though it was installed with the help of relatives who are electricians, the photovoltaic system cost $14,000, so it has a longer “payback” time –– approximately 30 years, he said. “We installed 1,800 watts of solar power with a state grant,” he said.

Even with tax credits, DiMauro said that price is probably too high for most people, but he expects costs will come down as materials are more widely available and more people learn how to install the systems.

DiMauro and his wife, Holly, live in Tiverton, near their eco-cottage. For many years the couple lived in Newport, and his business, DiMauro & Associates, was based in Jamestown. Their son, Ronald F. DiMauro, is an architect in Jamestown.

The State of Rhode Island offers a personal and corporate tax credit for residential solar and wind energy systems: 25 percent of the system cost, up to a maximum of $15,000. State law also exempts the systems from sales and use tax, and towns may opt to exempt them from property taxation.

Solar and wind energy systems are also eligible for a 30-percent investment tax credit from the federal government, thanks to the American Recovery and Reinvestment Act of 2009, which erased the previous maximum cap of $2,000 per system.

For DiMauro, the construction of the eco-cottage also delivered a less hopeful lesson: that, in his opinion, it is “impossible” for a developer in Rhode Island to build a house that meets “affordable” guidelines and still make a profit.

Even though DiMauro hunted for bargains on materials, and served as the general contractor for the eco-cottage project, the costs added up to $151,387 for building and $84,500, for the land, which amounts to an investment of $235,887.

“A contractor can’t build an affordable house and make a profit,” he said.

For more information on the ecocottage, see www.greenandsolarcottage.org

cdunn@projo.com