As a result of the ongoing conflict in Yemen, the country’s energy infrastructure and supply deficiency has worsened dramatically from its pre-existing poor levels, creating significant consequences for the population's essential needs. Recent estimates revealed that approximately 90 % of the people in Yemen had lost access to public power by 2020 leaving most of the country’s population in complete darkness. This study aims to design a cost-effective, and reliable energy supply system to repower Taiz city, in which the considered technologies are photovoltaic (PV), wind turbine (WT), diesel generator (DG), open cycle gas turbine (OCGT), battery (Bat), and converter. The developed energy system planning model was built in Microsoft Excel and employed to simulate and optimize four different energy system configurations. The resulting least-cost energy system comprises a 131.51 MW wind system, a 152.13 MW photovoltaic system, a 16.92 MW diesel generator, and 66,321 batteries (16,580 strings) with an associated levelized cost of energy (LCOE) of USD 0.166/kWh achieving 90 % carbon dioxide equivalent emissions (CO2-eq) reduction, and 40 % LCOE reduction compared to the conventional power system.