Very small hydropower (pico hydro) schemes, with an output of less than 5 kW, can be a cost-effective option for the electrification of remote rural communities. Despite the fact that each hydropower site is unique, there is potential for using standardised equipment and low-cost approaches to scheme design. Relatively low equipment costs are possible, particularly if locally manufactured in a developing country, which enable costs per unit of energy output to be lower than small petrol or diesel generators, wind turbines or PV systems. Nevertheless, it is important not to compromise on technical quality of pico hydro schemes, as this may lead to poor efficiency or long periods when the scheme cannot operate, which will affect the financial success of the scheme. In the longer term, inappropriate cost reductions may lead to reduced uptake of the technology. The challenge is therefore to provide engineering designs and implementation methods that can effectively be customised for a wide range of schemes. This paper describes research and development of successful approaches that have been used to enable pico hydropower to be implemented in diverse situations around the globe. It includes an analysis of penstock pipe sizing to achieve optimum economic design. (C) 2009 Elsevier Ltd. All rights reserved.