The objective of the present study is to verify the viability of implementing a diesel-generating group, which would work at peak times, in a grain-processing facility located in the town of Cascavel, in western region of Paraná, Brazil. The demand and consumption of electrical energy for the unit were determined for four operational scenarios. For each of these scenarios, the annual cost of using a diesel-fueled generator was compared to the cost of using electrical energy under three pricing systems. The criteria used for making investment decisions were the Internal Rate of Return and the Payback Discount method. It was determined the minimum annual use necessary for the implementation of a diesel generator to become viable. In the most critical scenario of the operation, the implementation of a generator becomes viable in the fourth year of use. The main results allowed concluding that implementing a diesel generator group at peak times is only not viable when using a conventional rate system and when demand and consumption are low.