The transition towards sustainable energy, championed by the Nigerian Electricity Act (2023) underscores the importance of solar energy and green hydrogen in tackling energy poverty in sub-Saharan Africa, especially in Nigeria. However, uncertainty remains among investors and government entities regarding the optimal geographic, technical, and economic conditions for utility-scale renewable electricity projects. To address this, an evaluation of two solar technologies-Photovoltaic (PV) and Parabolic Trough CSP technology (PT-CSP)-was conducted under specific geographical and techno-economic criteria to support solar electricity and green hydrogen development across Nigeria. The study estimated Nigeria's energy demand and employed site evaluation, Multi-Criteria Decision-Making, the Analytic Hierarchy Process (AHP), and Geographic Information System (GIS) tools, alongside the NREL System Advisory Model (NREL-SAM) for power plant analysis. Results indicate that 105.63 GWe of grid capacity is required to meet Nigeria's energy demand, whereas 57.32 GWe from grid-connected solar plants needed to replace unsustainable grid supplying 54.3 % of estimated population. Lagos requires the highest capacity (4.93 GWe), followed by Rivers, Kano, Oyo, and Ogun. Land suitability assessment identified 0.79 % (6815.68 km2) of Nigeria as highly suitable for solar-hydrogen projects, while 18.49 % (158,450.45 km2) is less suitable with most of Nigeria moderately suitable. Regions are ranked with the North-Central and North-East identified as most viable for PV and PT-CSP projects. A comparative economic analysis shows PV is superior in Nigeria, generating twice the energy output and costing six times less per unit of electricity than PT-CSP. These findings offer guidance for optimal solar energy and green hydrogen deployment.