The Dow Chemical Co. has developed a new roof shingle that doubles as a solar panel. The shingles, which can be incorporated into rooftops alongside traditional asphalt shingles, use low-cost thin-film cells of copper indium gallium diselenide. While Dow expects to profit greatly from the Powerhouse Solar Shingle — the company predicts it will bring in as much as $10 billion in revenue by 2020 — there will be significant benefits for consumers too. The innovative shingle is expected to cost 10% to 15% less than traditional solar panels and will be cheaper and quicker to install.