For the past year, the National Institute of Standards and Technology has tested photovoltaic roofing products on roofs in Maryland. And the results are rather encouraging – with solar power efficiency varying from 6 to about 16 percent.

Based on various kinds of roofing products – ranging from tile, slate, and the single most popular shingle, all have photo-voltaic cells and surrounding inactive areas where roofers can secure them the old fashioned way – with a hammer and nail.

However, the problem is that unless one lives in the deserts of Arizona and have their house built facing east to west, the angle at which shingle based solar energy collectors are placed, simply causes them to miss the majority of the incoming solar energy. Conventional solar cells are rack mounted and can follow the sun – thereby maximizing solar to electrical efficiency. But with roof-mounted shingles, the angle is static and as such, once the main force of the energy passes efficiency plummets.

Still, if this problem can be surmounted, the outlook can be particularly profitable. National averages for electric power are between 16 and 21 cents per kilowatt-hour. Tax benefits from deductions on solar energy collectors can lower it even more. And if you live in an area where power companies will purchase your excess electricity for the grid, then your green house can create much more than a diminished carbon footprint, it can create a bulging bank account.