Green hydrogen economy formation is a key element of Oman's strategy of economic diversification and decarbonisation in the context of Vision 2040. This study is a combined techno-economic and investment analysis of the green hydrogen production on a large scale in Oman through an alkaline electrolysis system that operates on solar energy within a 23-year project life. The financial model is designed in such a way that it can be used to estimate the levelized cost of hydrogen (LCOH) and determine the viability of the project based on discounted cash flow metrics, such as the net present value (NPV) and the internal rate of return (IRR). In contrast to traditional deterministic evaluations, time-based cost estimates, and an extended sensitivity model including discount rates, capital expenditure overruns, electricity, and water prices are included in the analysis as the main indicators of economic uncertainty in the Omani setting. Findings show that the LCOH will reduce significantly, with 6.37 USD/kg in 2025 decreasing to 2.85 USD/kg in 2050, which will be mainly due to the decrease in capital costs and the increase in the efficiency of operations. Financial viability is, however, very sensitive to financing assumptions and electricity prices, and IRR values are never greater than the assumed cost of capital under the base-case conditions. Commercial attractiveness would be very low without the support of policy. The findings indicate that although Oman has high potential of resource to develop green hydrogen, economic competitiveness will be attained through maximised financing regimes, variable electricity pricing systems, and supportive policy tools. This research adds to the body of literature by giving a clear, Oman-specific investment appraisal model that relates the techno-economic performance to the financial viability, providing practical implications to policymakers and investors.