By optimal sizing of a wind/photovoltaic hybrid renewable energy system, trimming the surplus capacity to reduce the fluctuations in the electricity supplied to the grid and using it to produce green hydrogen through electrolysis, a stable output with maximum possible capacity factor is generated to maintain the electricity grid stability. Simultaneously, the trimmed energy is used in a secondary conversion path that minimizes the weighted average cost of energy generated from the entire plant. This surplus power-to-gas conversion allows the use of green hydrogen to produce electricity, methanol, or ammonia subject to the resource availability, site characteristics, and financial feasibility. Based on robust site selection criteria, the best performance is obtained at two sites: Ras Ghareb and Minya achieving the least energy cost with some variance in their performance. For Ras Ghareb site, the optimally sized renewable energy plant provided the grid with a quasi-steady capacity of 423 MW with a capacity factor of 80.04 % and was capable of injecting 2965.86 GWh throughout the year with the least cost of 2.4355 ¢/kWh. A surplus of 3.9 % of the total energy produced from the plant was directed to produce 1922-ton H2/year, achieving the least cost of hydrogen production of 1.9745 $/kg H2. For the other selected site, Minya, the clipped energy is used to produce 3330.47-ton H2/year with an optimized least cost of 3.5268 $/kg H2. The difference in hydrogen cost was attributed to the number of full operating hours of the electrolyzer in both sites. The cost is mainly affected by the electricity price and the electrolyzer cost. With both tending to decrease, future forecasts show hydrogen cost reductions.