<![CDATA[Reservoirs that already support hydropower and water supply are increasingly viewed as sites for floating photovoltaic (FPV) development, a pairing that speaks directly to SDG 7 (Affordable and Clean Energy) and SDG 6 (Clean Water and Sanitation). Taking Sutami Reservoir in East Java as a case, this study examines an FPV layout occupying 5% of the reservoir's normal water surface area (602.499,80 m²), with attention to electricity yield, evaporation-related water savings, and financial viability. Energy output was estimated from irradiance and module-efficiency parameters, evaporation savings were derived from the change in exposed surface area, and feasibility was judged through four standard indicators: Net Present Value (NPV), Benefit-Cost ratio (B/C), Internal Rate of Return (IRR), and Payback Period (PP). At an installed capacity 100 MWp, the system is projected to generate 175.80 GWh annually—about 23,89% of the existing hydropower plant's output—while conserving roughly 2,48 million m³ of water per year, a 54,61% gain in raw-water benefit. The economic analysis is less clear-cut: NPV comes to Rp 26,03 billion and B/C reaches 1,01, but IRR sits at only 7,1% and payback stretches to 23,30 years against a 30-year assumed project life—leaving roughly seven years of net benefit at the end, a narrower window than the headline numbers suggest. Taken together, the results point to real technical benefits from combining energy generation with water conservation at Sutami Reservoir, though the thin economic margin warrants a closer sensitivity analysis before the project moves toward implementation]]>
