A thermo-economic model performed by the International Atomic Energy Agency, is used to measure and compare the efficiency of two desalination low-temperature technologies: multistage flash (MSF) and multi-effect distillation (MED) in dual-purpose power/desalination plants based on gas turbines, The power plant is initially planned:to supply the electricity demand during peak periods in the south of Tunisia, A desalination plant is used to recover part of the heat from the turbine exhaust gases. A solar pond stores the rest of the heat and restores it to the desalination plant the rest of the day. It is found that the increase of the power plant leads to more important water production quantities. The use of 120 MWe gas turbine coupled to the MED technology permits to reach attractive costs around 0.5 US $/m(3). A simulation of replacing the power plant by a standard solar pond is also conducted in order to evaluate the role of renewable energy in the remote regions.