The generation of most electricity produces enormous amounts of heat which is typically wasted - literally up the chimney.
Cogeneration - or "Combined Heat and Power" - systems make use of this otherwise wasted heat to warm buildings. Much of Manhattan is heated this way courtesy of several con-edison plants in the vicinity. It's a brilliant solution to improve energy efficiency in an urban area, but doesn't work so well in less urban areas. There, people typically rely on their own natural gas furnaces to heat their homes. But what if you could reverse the cogeneration idea? Imagine taking an already efficient gas furnace and generating a home's electricity directly from it, while it heats? That's the reality that Marathon Engine has in store for the North American market today. While not quite a start-up (they've been selling units in Europe for 5 years), the company's "EcoPower MicroCHP" units look set to sell well, despite, or perhaps because of the economy downturn. Read more here at triplepundit