Natural-gas fired reciprocating engines are also used for on-site electric generation. These types of engines are also commonly known as combustion engines. They convert the energy contained in fossil fuels into mechanical energy, which rotates a piston to generate electricity. Natural-gas fired reciprocating engines typically generate from less than 5 kW, up to 7 megawatts (MW), meaning they can be used as a small scale residential backup
generator to a base load generator in industrial settings. These engines offer efficiencies from 25 to 45 percent, and can also be used in a CHP system to increase energy efficiency.
Fuel cells are becoming an increasingly important technology for the generation of electricity. They are much like rechargeable batteries, except instead of using an electric recharger, they use a fuel, such as natural gas, to generate electric power even when they are in use. Fuel cells for distributed generation offer a multitude of benefits, and are an exciting area of innovation and research for distributed generation applications.