Zero-energy city, sustainable City and zero-carbon city are new terms in cities’ energy management. In this study, a framework of designing a Low-Carbon Eco-City (LCEC) in urban sector of Mashhad with focus on sustainable supply of electrical energy has been simulated. For this purpose, the maximum potential of biomass renewable electricity and expansion of photovoltaic capacity- required to cover remaining electricity demand in urban sector of Mashhad has been entered in Hybrid Power Generation System by using an analytical programming approach. The results indicated that biomass technology is superior technology for designing LCEC with less volatility and lower cost of production and it enters into the fossil-renewable hybrid production system with high penetration. Despite increasing capacity of photovoltaic technology up to 8GW, because of high investment cost problem, photovoltaic power generation cannot utilize in competition with the production of biomass technology. Hence it is suggested that biomass technology of sustainable development energy in the urban sector of Mashhad to be regarded as a city on the path LCEC. On the other hand, supportive policies should be adopted to reduce the cost of photovoltaic technology in order to provide the competitiveness of this technology in high capacities.