A techno-economic study for dual purpose combined cycle gas turbine and steam turbine power generation, with desalination plants in the vicinity of Sharm El Sheikh of about 500MW and about 25 MIGD potable water is presented. The following was taken into consideration: size of gas turbine; heat recovery steam generator (HRSG) (dual pressure); suitable type of steam turbine (back pressure) to produce reasonable power production and match the required water production; suitable type of desalination (MED-TVC type). The study involved heat and mass balance for HRSG and steam turbo generator, power and desalination configuration and phasing, financial internal rate of return (FIRR) for each phase for three cases as follows: 1) Case 1 (bigger power and desalination units): two gas turbines (190 MW ISO each), and two back pressure steam turbine each of (54.3 MW), two HRSG, and four desalination units of 5 MIGD each in two phases; 2) Case 2 (bigger power and desalination units): two gas turbines (169.2 MW ISO each), and two back pressure steam turbine each of (48.2 MW), two HRSG, and four desalination units of 4.5 MIGD each in two phases; 3) Case 3 (smaller power and desalination units): four gas turbines (123.4 MW ISO each), four HRSG, four auxiliary boilers, two back pressure steam turbines of 67.6 MW, and eight desalination units of 3.5 MIGD each in four phases. The technical, economical and financial studies show that the project is feasible at production tariff of US$ 0.025/KWH and US$ 1/m3 with comfortable (FIRR) margins. Sensitivity between FIRR and different tariff rates is presented. Keywords: Power, Desalination, Economics, BOO, Development.