A review of small hydropower performance and cost

Small-scale hydropower (SHP) is attracting international attention as a reliable and flexible renewable energy option. In the United States, federal agencies have recently examined new SHP sites for development and assessed existing non-powered dam infrastructure for additional generation capacity. Hydropower decisions are informed by the cost, feasibility, and performance of different project options. This review is the first to: 1) categorize different types of SHP and the variety of specific cost and performance metrics used to evaluate projects; and 2) compare the cost and performance results (annual capacity factor, project power capacity, net present value (NPV), benefit-cost ratio, and levelized cost of energy) for 13 SHP studies in multiple countries spanning four continents, using diverse generation technologies and technoeconomic assessment models. Cost estimates in different currencies and dollar years are harmonized to provide comparable data ranges and simple calculations and statistics (e.g., NPV: $-1.8 to $30 million total; -$551,382/kilowatt (kW) to $11,502/kW; $3,609/kW mean; $2,655/kW median). General trends are documented in the SHP literature (i.e., decreasing levelized cost of energy and increasing benefit-cost ratio with increasing power capacity), but there is a striking lack of consistency in reported detail, assumptions, definitions, and data inputs. Similarly, there is much variability in key input parameters (e.g., capacity factor, discount rate, project lifetime, etc.), which limit meaningful comparisons across studies and highlight a need for more publicly available, user-friendly, and free SHP cost estimation tools with site-specific default input data, user-defined flexibility, and uncertainty analysis.