For the purpose of practical realization of HDR, the power output and generation efficiency of HDR at the two promising Japanese sites are calculated under the condition of utilizing hot water from hot rocks of average depth 3,000m and average temperature 300℃. For the calculation, we adopted single flash type geothermal power plant for surface system and estimated the intrinsic flow rate of water taken from rivers in the area.
　We obtained the results that electricity output increases in proportion to the flow rate of water and electricity output 1GW requires amount of water 2.4m3/s (i.e., 76 Mm³/y). When HDR plants generate 20% of total annual Japanese energy (=200TWh/y (i.e., 30GW)), necessary amount of water is 2.3 Gm³/y. Total amount of water in Japanese rivers is 240 Gm³/y, and 168 Gm³/y is available except agricultural, industrial and daily life use. We can conclude that above mentioned amount of water is realizable.
　Electricity cost of HDR system with improving the water recovery up to 98 % is almost equal to the cost of a conventional geothermal power calculated in the previous paper.