Generators are used for electric power generation. Two categories of diesel generators are basically available in market- one is portable generator and the other is standby generator. Diesel Generators are mostly used to make sure that electric appliances can be run when there is a power failure. Standby diesel generators are mostly used in homes and offices and installed outside the house or office building. These are plugged in home wiring or electric power circuit. These can automatically detect power failure and start supplying power with in moments. Portable diesel generators are used on sites where there is much less supply of electric power and they can only run few small appliances like refrigerators, televisions and turnaces. Diesel generators use comparatively less fuel and thus are more fuel efficient than power generated by gasoline or natural gas. For every liter of fuel consumed, diesel generators can run 2 to 3 times more efficiently than natural gas engines. There is no need of frequent maintenance for diesel engines, but gasoline engines need more frequent maintenance. Most diesel engines designed with water-cooled engine up to a speed of 1800 rounds per minute. This makes sure that the engine is durable, and makes it most dependable of all generators. Unlike other natural gas generators and gasoline generators, diesel engines are very safe to use because they work on direct injection principle and they do not have any spark plugs. The unavailability of spark plug keeps them safe from fire. Diesel generator has a better shelf life. This is the least flammable source of fuel, hence can be stored for more time. The fuel for the diesel generators is available at all gas stations and can be collected in comfortable cans. Main problems in case of diesel generators are: it is very hard to start them in cold weather, they are noisy and emit more smoke. Home diesel generators may cost $ 800 for 4 kilowatt to $10000 for a 15-kilowatt depending upon the rating, voltage consumption, quality and brand name. Diesel generators can also be used in industrial purposes. For industrial purpose they are available in range of 500 kilowatt to 2000 kilowatt. Fuels such as diesel, gasoline, natural gas, or propane can basically power home generators. Some models of diesel generators also designed with multi fuel capabilities. The fuel choice of will depend on availability of fuel during emergency times.