Potatois thefourth most important food croin the world, and very important for long-term food security. In the other hands, improving theenergy efficiency and moreefficient useof farminputs alsocadecrease thedestructioofatural resources and develop sustainable agriculture as an economic systems. Thifield studywaconducted to evaluate the energy use efficiency and nitrate concentration (water, soil and tubers) forthreegrouofotato farms (small: 0.5 ha; medium: 0.5-1 ha, and large: 1 ha) in theFereydaregion of Isfahan Province, Iran. Data used in this study were obtained from 30 potato farms using face to face interview and semi-structured questionnaire during 2013. The nitrate concentration of irrigation water and soil were measured before planting date and after harvesting time. Also, the nitrates concentration of potato tubers were determined for three farm sizes. Total energy inputs involved in the small, medium and large farms were calculated as 70,342 MJ ha -1 , 63,386 MJ ha -1 and 56,745 MJ ha -1 , respectively. The comparison based on farm size showed that medium (10%) and large (20%) farms used lower amount of energy input consumption than small farms, respectively. On small farms, fertilizers account for 35.1% of the total energy followed by seed tuber (21.4%) and water irrigation (19.0%). In the medium farms, fertilizer is the most energy consuming (36% of total energy) followed by seed tuber (20%) and diesel fuel (18%). On large farms, fertilizer account for 31% of the total energy followed by diesel fuel (23%) and seed tuber (19%), respectively. Comparing the farms sizes, the water irrgation and seed tuber were greater in the small farms by 31% and 26%, while, the fuel consumption of large farms was more than the small and medium farms by 14% and 11%, respectively. Renewable energy represents 45.5% in small farms operations, 41.9% in medium farms operations and 41.8% in large farms operations. Direct energy was greater in the large farms than small and medium farms by 7% and 3%, respectively. The averaged potato yield of small, medium and large farms systems were 22, 24 and 26 tons ha -1 , respectively. Total energy outputs were 79,200 MJ ha -1 for the small farms, 86,400 MJ ha -1 for the medium farms and 93,600 MJ ha -1 for the large farms. The energy use efficiency was 1.12 for the small farms, 1.36 for medium farms and 1.65 for large farms. After harvest time, the NO 3 -concentration iirrigation water was above the standard value (45 mg L -1 ) in 87% of small farms and 85% of medium farms, while in the all large farms was up to standard. NO 3 -concentration i soil of 76% medium farms and 59% of large farms was above the standard value (20-22 mg kg -1 ), while in the all small farms was up to standard. The average concentratioof NO 3 - iotato tuber was lower in the large farms than small and medium farms, respectively. NO 3 -concentration in potato tubers of 49% of small farms, 26% of medium farms and 17% of large farms was above the standard value (250 mg kgFW -1 ). NO 3 -N in water irrigation and tubers had the significant ( P ?0.01) and positive correlation with nitrogen fertilizers and irrigation water consumption and adverstly negative correlation with manure. Energy efficiency had negative and significant correlation with nitrate concentration of water and yield of potato tuber. The lowest concentration of NO 3 -N in potato tubers were observed in the late-season potato cultivar that may producehigher tubers yield (cv. Agria). Key words: Chemical fertilizer, Cultivar, Energy efficiency, Nitrate, Potato, Sustainable agriculture, Tuber