Final answer:
Generators of over 15 kW generally use diesel, natural gas, or propane, with diesel being the most common for small-medium units. Natural gas power plants are highly efficient, and propane is noted for portability and storage. Solar power is less common in large-scale generators above 15 kW.
Step-by-step explanation:
Generator units with a capacity greater than 15 kilowatts typically use diesel fuel, natural gas, or propane as an energy source. Diesel is commonly used in smaller electrical generators, particularly in remote areas or as backups for electrical distribution system failures. While larger power plants often use coal, natural gas, or nuclear power, small to medium-sized generators tend to select diesel because of its energy density and reliability. Natural gas fueled power plants burn fuel directly in turbines resembling jet engines and have high efficiency of almost 60% due to higher operating temperatures. Propane is also utilized for its portability and easy storage, albeit less frequently than diesel and natural gas. In contrast, solar power typically pertains to individual solar cells or panels rather than large-scale generators above 15 kW.