On a hot sunny day in late May, a roofing crew arrived at the Madrigals’ home near Sacramento for a rather unusual job. Taking out what appeared at first to be typical shingles out of cardboard boxes, workers pounded nails into what were in fact sheets of solar cells covered in thin glass. When completed, the Madrigals got a new power-generating roof and became the first customers in California for Dow Solar’s hybrid shingles.

The 5.47-kilowatt system will help Frank and Cyndy Ann Madrigal cut their monthly utility bill by about two thirds. The couple and their four children live in a 3,000-square-foot, split-level home with a swimming pool in Folsom, Calif., where summer temperatures are in the steamy 90s (Fahrenheit). Their monthly bill runs from around $150 to over $500 throughout the year.

“We needed a roof and some way to make our electricity affordable. We wanted to integrate the two,” Cyndy Ann Madrigal said.

After years of touting the merit of combining solar cells with roofing materials and delays in launching the solar shingles, Dow finally began selling them, first in Colorado last fall and then in California and Texas this year. The idea of embedding solar cells in roofing materials isn’t new. But doing it well – from ensuring the solar cells are well protected to making the hybrid shingles easy to install and still function as part of a roof – is no small feat.

The market has seen some solar cell-embedded tiles, shingles and other slow-profile solar panel installations that try to mimic the appearances of residential roofing materials. But they haven’t been popular for a variety of technical, warranty and cost issues.

Dow uses a type of solar cells and design that are quite different from the vast majority of the solar panels that sit on residential rooftops today. Instead of using silicon cells, which are thicker and could crack under heavy weight, Dow opted for ultra-thin and more pliable cells made with a mix of copper, indium, gallium and selenium (CIGS). Global Solar Energy in Arizona is supplying the CIGS cells to Dow, which then assembles them into shingles at its factory in Michigan.

A knotty problem that Dow had to solve involved hiding the electrical wires for connecting the shingles to one another. The wires must fit within the thin profile of the shingles or else the solar shingles will stick out next to the regular shingles. Dow buried the wires within each shingle and created a connector at each end to string the shingles together (see the photo slide below).

“We developed a unique, plug-style connector that allows us to connect the shingles without the need to tuck the wires under the shingles or under the deck,” said Dan Pezolt, North American marketing at Dow Solar, which is part of Dow Chemical Co. “That connector philosophy is what allows us to install directly to the roof deck.”

Dow’s entry into the solar shingle market has been highly anticipated partly because, unlike a startup, Dow presumably has the technical, financial and marketing muscles to achieve success at making and selling a novel product. The company received a $20 million federal grant in 2007 to integrate solar cells into building materials, and the hybrid shingles are the first product from that research. Last year, U.S. Department of Energy awarded Dow $12.8 million to develop more and cheaper solar building materials.

It’s too early to tell whether solar shingles will become a successful product for Dow. The price of conventional solar panels has dropped considerably in recent years, and financing products such as leases – where consumers pay only for the solar electricity and not the expensive equipment – have made it more affordable for homeowners to go solar. Dow is looking at how leases might work for its solar shingles, and there are legal questions about whether a financing institution could own a solar roof in the same way that they own the solar panel system in a lease.

Dow is producing shingles in a limited quantity at a pilot line. It’s building a larger factory, also located in Midland, Mich., and plans to start producing shingles there in early 2013, Pezolt said. He declined to disclose the new factory’s production capacity, which would provide a clue to the company’s sales forecast.

Roofers install the solar shingles the same way they put regular shingles in place – by nailing them directly onto the roof deck. Each shingle comes with an adhesive to bind one to another. A big selling point of solar shingles is their unobtrusive appearance, unlike conventional, rack-mounted solar panels, said Jeffery Tamayo, director of operation at Town & Country Roofing. He had just sold his fourth solar roof when he and his crew were working on Madrigals’ roof project.

Aesthetics certainly helped to make solar shingles a more attractive option for the Madrigals. A strong wind that toppled a solar water heating system on a neighbor’s roof also nudged the couple to consider something that would sit low on top  of their home. Frank Madrigal first read about the solar shingles two years ago, and he and his wife decided to wait for Dow to start offering them.

“I saw a drawing of what (the solar shingles) would look like, and it hit me that they would be way more attractive than having big old solar panels,” Frank Madrigal said.

The couple said a reroofing project that also included solar shingles made the most financial sense for them than simply adding solar panels. Including incentives from their utility and a 30 percent federal investment tax credit, the roofing project cost around $44,100. They obtained an equity line of credit to finance two-thirds of the cost of their new roof, and the rest came from their own cash.

Electricity from the solar roof should reduce the Madrigals’ electric bill by two thirds because it will in effect move the family off the top – and most expensive – tier of electric rates and offset some of the energy use at lower rates as well, Cyndy Ann Madrigal said. The couple expects to pay off the cost of the entire roof project within 15 years. Dow’s warranties run 20 years and guarantee that the solar shingles will produce at least 90 percent of their expected power output within 10 years and 80 percent for the remaining 10 years.

The family has yet to start enjoying using solar electricity, however. They are waiting for their solar electric system to be connected to the grid, and the process of gaining approval and turning on the system by their utility, the Sacramento Municipal Utility District, would take about six weeks. That wait, Cyndy Ann Madrigal wrote in an email “is ridiculous since we are all set up and ready to go and it is HOT!!!”