In order to spread the small/medium-scale hydroelectric power generations, the costs of power generations must be reduced to 1/3 of the current costs. Construction costs are roughly classified into electrical construction costs and civil engineering construction costs. Since the candidate site is about 20,000 locations, each cost reduction can be expected by the standardization and mass production. In the previous report, we showed the possibility to reduce the electrical construction costs to 1/3 of the current situation, by standardizing the hydro turbines and generators with analyzing of the materials costs. In this paper, we tried to calculate the overall reduced construction costs by applying the cost down methods of (1) usage of appropriate materials and (2)employment of the general standard unit prices of mass production to civil engineering costs. As a result, it was found that it is possible to reduce the power generation costs to less than the 15 yen/kWh which is the 1/3 of current costs.
　National annual generated energy of small/medium hydroelectric generations is estimated to 47 TWh by Ministry of the Environment under the assumption of 60% energy abailability factor. This value can be increased to 58 TWh by increasing the maximum flow rate although energy abailability factor reduce to average 40% from 60%.
　In future, we propose for the dissemination of small/medium-scale hydroelectric generations, by investigating each individual site condition and appropriate construction method.