ABSTRACTReliable power supply provision for customers is very important for electrical energy providers. The emergence of regional energy networks (RENs), and electricity market developments add to the above challenges. RENs consist of natural gas and electricity as inputs and energy storage systems (ESSs), combined heat and power (CHP) systems, thermal energy storages (TESs), boilers, photovoltaics (PVs) and wind turbines (WTs) as resources. In this paper, a risk‐based expansion planning model is developed for RENs considering operation and investment costs. PVs and WTs power generation, demand response (DR), and failures of tie switches between REN and distribution networks are defined as RENs operation uncertainties. Reliability index is formulated and Probability‐Tree tool is used for scenario generation. The mentioned optimization problem is solved using a genetic algorithm (GA). We use 25‐Bus IEEE standard distribution network to verify the efficiency and performance of the proposed model. Two RENs are connected to the test system and simulation results are obtained for two case studies. Simulation results show that if the probability of failure of tie switches is considered, the investment and operation costs of RENs are increased by about 92% in the planning horizon.