Techno-economic assessment and investment conditions for a hybrid small hydropower–rooftop solar photovoltaic system in Ghana

Attaining Sustainable Development Goal 7 (SDG7) requires reliable and affordable electricity, yet Sub-Saharan Africa continues to face persistent challenges of access, cost and supply reliability. In Ghana, thermal plants account for roughly 68% of electricity generation, sustaining high tariffs and greenhouse-gas emissions despite abundant renewable resources. This study investigates when and under what conditions an integrated small hydropower–solar photovoltaic (SHP–PV) hybrid system is the preferred investment over standalone rooftop PV, using Asantekrom in Ghana’s Tano River Basin as a planning-level case study. Using a flow-duration-curve assessment with an environmental-flow allowance, a run-of-river plant rated at 4.4 MW delivers about 22.4 GWh/year at a capacity factor of approximately 0.59 — consistent with peer-reviewed firm-energy estimates for the basin (4.6–46.4 GWh per site) — while a GIS-based rooftop survey of 102 structures supports a 2.6 MWp photovoltaic system generating about 5.06 GWh/year. The two resources are seasonally complementary (monthly generation correlation r = −0.59), and the combined annual output of about 27.5 GWh shows lower variability than either source alone. The central finding is that at the current bulk-supply tariff of GHS 0.921/kWh, standalone rooftop PV is the superior investment (NPV GHS 18.7 million, LCOE GHS 0.50/kWh), while the hybrid is viable but strictly inferior (NPV GHS 15.8 million, IRR 11.2%, LCOE GHS 0.86/kWh) because adding the loss-making hydropower plant destroys GHS 2.9 million in value. The hybrid becomes the dominant investment above a tariff crossover of approximately GHS 0.94/kWh — just above the current tariff — or under concessional finance (discount rate ≈ 8%). At the avoided thermal generation cost of GHS 1.26/kWh, the hybrid NPV reaches GHS 99.8 million. A multi-parameter sensitivity analysis (tornado diagram) and a two-way tariff–discount-rate matrix identify the conditions under which each configuration is preferred. A complete one-month shutdown of hydropower in February is identified as a critical operational risk. The study contributes a documented, site-specific comparative framework that quantifies when hybridisation adds value, providing evidence-based guidance for policy and investment decisions in Ghana’s electricity sector.