This study evaluates the integration of MSF, MED, and SWRO desalination systems with a Combined Cycle Power Plant (CCPP) to optimize fuel efficiency for the co-production of electricity and desalinated water. A thermodynamic approach is utilized, modeling the integrated system as a single unit with one fuel input and two outputs: electrical power and potable water. The standalone CCPP achieves 59.8 % efficiency, but this decreases when desalination units are integrated due to energy diverted to water production. Among thermal methods, MED proves more efficient than MSF, reducing fuel consumption by approximately 3 % and lowering water production costs by up to 19 %. In contrast, SWRO, which relies solely on electricity, demonstrates a 52–62 % reduction in energy cost compared to thermal methods. Hybrid MED-SWRO systems optimize fuel use, with the MED3RO7 system (30 % MED, 70 % RO) achieving the best performance, cutting water production costs by about 30 % relative to standalone thermal systems. The analysis reveals that shifting from MSF to MED, supported by HRSG, significantly reduces thermal energy consumption, positioning MED as a more cost-effective alternative to MSF. Hybrid systems enhance overall fuel efficiency and economic viability in dual-purpose power plants. • MSF raises fuel use by 13–18 % in CCPP; MED cuts thermal demand by 30 %. • SWRO achieves lowest water cost at $0.308/m³ in cogeneration systems. • Hybrid MED-SWRO optimizes fuel efficiency and water yield in CCPP. • HRSG enhances MED’s cost-effectiveness over MSF in dual-purpose plants. • Thermodynamic model treats CCPP as one input, two outputs for efficiency.