There are rooftop solar panels, and then there are roofs that are solar panels. The difference isn't enough to stake a market on.

Dow Chemical Company is cutting off its solar shingle line, the Powerhouse Solar System 2.0, reported MLive. The company will sell its last systems on July 28 and ship them out by August 10, less than five years after it launched the product.

The demise of the business reflects the difficulty of building-integrated photovoltaics (BIPV), which incorporate solar modules into construction materials. These systems tend to replicate the purpose of a rooftop solar installation -- but with less efficiency, which makes it hard to sell in the long run.

Even the Powerhouse marketing material had trouble articulating why it's better than conventional rooftop PV. The product website claims the Powerhouse "completely changed the way the world looks at roofs" because "instead of merely lying passively on your house, these shingles generate electricity from the sun’s rays to power your life."

You know, kind of like solar panels.

The stated argument for choosing solar shingles instead of conventional PV modules is less grand: "Unlike other solar alternatives, everything in your Powerhouse system is provided and backed by Dow." If that doesn't sell a customer, perhaps the aesthetics will. The shingles integrate flat on the roof, instead of popping up from the surface of the building. The concept simplifies solar installation, too, by combining it with roof construction.

The problem is that solar shingles generate electricity on a roof much less efficiently than solar modules. There's an environmental appeal to wringing every last bit of use out of the built environment, but it doesn't change the fact that rooftop or distributed solar PV does the job better.

Once the conventional PV sites are tapped out -- if that ever happens -- the value of solar-generating windows, walls and roads will increase. Until then, BIPV frequently amounts to paying a premium for less of a return. That math has already killed a long line of companies.

The shingle shutdown also resulted from the internal dynamics at Dow. The massive corporation is reorganizing in advance of a merger with fellow giant DuPont, and that includes cutting 2,500 jobs worldwide. A Dow spokesperson told MLive that "a majority of positions in the Dow Solar business will be impacted by the restructuring."

The decision also marks a blow to NuvoSun, which produces the flexible CIGS (copper indium gallium selenide) panels used in the shingles. The late 2000s saw an influx of billions of dollars in investments for CIGS companies, very few of which still stand or produce serious capacity (Remember Solyndra?).

NuvoSun was one of those survivors, acquired by Dow in 2013. It offers a standalone flexible solar cell, but it remains to be seen what the company will do once the shingle application cuts off.