Currently, biomass contributes to approximate to 14% of global energy needs. Therefore, many studies and policies have been developed in order to expand the participation of renewable energy in the global energy matrix. In this context, ethanol has received substantial interest. This work investigates ways to improve efficiency in ethanol production from sweet potatoes, considering the costs that make the process potentially implementable. The following aspects were investigated: (i) conversion efficiency according to the post-harvest time; (ii) influence of the heating method (water bath (conventional) and microwave) as well as the corresponding processing costs. The conversion efficiency increased significantly during sweet potato ripening, where the highest value was achieved 25 days after harvest. This is a very important result since it has a strong impact on the final cost. Among the heating methods, the conventional one was slightly superior in terms of conversion efficiency (9% higher at 25 days) and also had better results regarding cost analysis. Among four designed scenarios, the largest cost difference was 17.5%. Instead of a definitive elimination of microwave heating, the results should be analyzed to identify where the microwave heating should be improved in order to make it more attractive in the future.