Book excerpt: Micro-Hydro Design Manual has grown from Intermediate Technology's field experiences with micro-hydro installations and covers operation and maintenance, commissioning, electrical power, induction generators, electronic controllers, management, and energy surveys.There is an increasing need in many countries for power supplies to rural areas, partly to support industries, and partly to provide illumination at night. Government authorities are faced with the very high costs of extending electricity grids. Often micro-hydro provides an economic alternative to the grid. This is because independentmicro-hydro schemes save on the cost of grid transmission lines, and because grid extension schemes often have very expensive equipment and staff costs. In contrast, micro-hydro schemes can be designed and built by local staff andsmaller organizations following less strict regulations and using 'off-the-shelf' components or locally made machinery.