Another form of distributed generation is combined heat and power systems. This micro-turbine from runs on natural gas to produce both electricity and heat. It's 82 percent efficient and has far lower levels of nitric oxide and sulfur oxide compared with diesel generators. The heat can be used for space heating or, with an absorption chiller, for cooling. Several are already installed in New York City in buildings, and a few have been tested in buses. It can also be configured to run off of methane from landfills or waste water treatment plants, according to the company.