Generally, the capacity of diesel power plants is between 2 to 50 MW is used in central power plants to meet peak demand in steam power plants and hydroelectric power plants. But nowadays, due to the high cost of fuel, diesel engines are not used for such applications.
The advantages are these :
Sturdier build construction with stronger metals, larger engines & cooling components
Lower maintenance costs due to lack of spark plugs for spark-ignition
Lower noise output and less overall maintenance when compared to natural gas generators
Longer overall lifespan & longevity
Efficient fuel consumption
Longer service & maintenance intervals when compared to natural gas generators