In recent years, the population growth has caused the water and energy shortages. Therefore, the current paper proposes a novel method for day-ahead optimization of integrated water-heat-electricity systems with the aim of minimizing the fuel cost of the desalination, heat treatment and power production units. The technical limits of the power only units, combined power and water generation units, cogenerators of heat and electricity, heat only units, and the seawater purification process are incorporated in optimization problem. In addition, a real-time demand side management strategy is applied on heat, pure water and power loads to reduce the objective cost function as low as possible by shifting a percentage of each demand from peak periods to mid or off peak hours. Moreover, aggregators of pure electric vehicles participate in bulk energy management by charging electricity during off-peak low-price hours and discharging it over the on-peak high-price periods. To validate the feasibility and cost-effective performance of the water-heat-power hub system, a mixed-integer non-linear program is developed by generalized algebraic mathematical modelling system (GAMS) optimizer and solved by branch-and-reduce optimization navigator (BARON) tool. The ramp down and ramp up limits of the thermal power plants, generation capacity of water/heat/power producers, and the load-generation balance criterion are considered as optimization constraints. It is found that $659,573 cost saving is obtained due to participation of PEVs and DRPs in trigeneration process. (C) 2019 Elsevier Ltd. All rights reserved.