The article highlights an important scientific and technical problem: increasing the operation efficiency of the diesel generator power plants. One of the possible solutions of the problem is developing the diesel generators that operate in a variable speed mode with shared loads on the power plant. Introducing such diesel power plants into practice in recent decades has become possible due to the necessary converting semiconductor equipment, as well as a significant increase in prices for hydrocarbon fuels and objectively formulated requirements to improve the environmental performance of technical complexes. There is presented a comparative analysis of the energy efficiency of two power plants: with classic diesel generators and with a variable speed diesel generator. It has been proposed to compare the energy efficiency of the power plants by calculating the specific and absolute fuel consumption. The method of determining parameters of fuel consumption is considered. The method is based on using a multi-parameter characteristic of a diesel engine and the values of the efficiency ratios of the elements of the power equipment of plants. The results of calculating the specific fuel consumption of the power plants when changing the load power subject to the operating mode of the generators are presented. The results confirm the energy efficiency of the power plant with a variable speed diesel generator. Efficiency is increased due to saving the hydrocarbon fuels. The maximal savings correspond to the power plant operation under the load 20% less than the nominal.