The study assesses the impact of the economic size of farms on the efficiency of their material and energy expenditure, based on 679 farms from the Lubelskie Voivodeship. The analysis was made for the years 2013-2015 and the farms were divided into six economic size classes. 5 indexes for the efficiency of material, energy and material-energy expenditures were calculated for all farms. The aim of the work was to select a group of farms with the highest efficiency of energy and material expenditure. It was found that economically small farms managed this expenditure most effectively, as evidenced by the highest values of 4 out of 5 analyzed indexes. Very small and medium-small farms demonstrated the highest efficiency of material expenditure. In contrast, energy expenditure was most efficiently used by medium-small farms. The farms that were the largest economically were characterized by the highest efficiency index of material and energy expenditure, calculated as the ratio of total production to the expenditure.