Where a small hydro power resource exists, experience has shown that there is no more cost - effective, reliable and environmentally - sound means of providing power than a small hydro power system. There are many hilly or mountainous regions of the world where the grid will probably never reach,but which have sufficient hydro resources to meet basic domestic needs of the local populations.The data pertaining to system costs, operation, maintenance and other relevant cost details are readily available along with the informative case studies. The For a realistic estimate it is important to capture uncertainty in systems and hence mathematical modeling and simulation studies have to been couraged in the field of energy studies. It is important for policy makers and modeling experts to study the systems collectively with other allied interdisciplinary sciences for a clear representation of the energy problem and effective implementation of the solutions. Researchers all over the world are working overtime to devise simple and efficient methods of utilization of renewable / small hydro - power resources more and more.