Click the image to go to the story in the always-informative Green section of the New York Times website:

When photovoltaic cells make electricity from sunlight, they collect a lot of heat along the way. And they don’t work as well warm as they do cold.  Four years ago I wrote about a hybrid system that was intended both to make electricity and gather usable heat on residential rooftops. That company, now called Echo Solar, is offering its product around the country.