Fuels such as gasoline, diesel, propane or natural gas basically power home generators. Some models also have multi fuel capabilities and run on gasoline, propane or natural gas. The choice of the fuel will depend on the availability of the fuel in times of emergency, fuel consumed per kilowatt of power produced, maintenance of the generator and the comparative risk of storing the fuels.

Diesel generators consume comparatively less fuel per kilowatt of electricity produced and more fuel-efficient than generators powered by natural gas or gasoline. For every gallon of fuel consumed, diesel generators run 2 or 3 times longer than gasoline engines. Diesel generators do not require frequent maintenance, as is the case with gasoline generators and are designed to run continuously for long hours. Most generators come with a water-cooled engine with a speed of 1800rpm. This ensures the engines durability, and at the same time, makes it the most dependable of all the other types of generators.

Unlike gasoline generators, diesel engines are safe as they work on the principle of direct injection and have no spark plugs, which keep them relatively safe from potential fire. Diesel has a longer shelf life, and being the least flammable source of fuel, can be stored for more than a year.

Diesel is available at most of gas stations and can be conveniently carried in cans. However, diesel generators are hard to start in cold weather; emit more smoke and are noisy. Home diesel generators may cost anywhere between $1000 for 4KW to $9000 for a 15 KW depending upon the quality, wattage rating and voltage rating. Diesel generators for industrial use are available in the range of 500KW to 2000KW.