The Climate Energy Micro-CHP System combines Climate Energy's state of the art high efficiency gas furnace or boiler with a proven natural gas engine/generator module designed and manufactured by Honda Motor Company of Japan. This combination provides unrivaled total energy efficiency in combined heat and power delivery.
http://www.climate-energy.com/micro-chp.asp The Ecopower Micro-CHP: Neat, Efficient and Easy to Maintain.
Principle
A Combined Heat and Power (CHP) unit basically produces electrical power with a combustion engine. The heat, which is normally lost in vehicles, for example, is recovered from the generator, engine and exhaust system and can be used for local heating purposes.
http://www.marathonengine.com/cogeneration.html