Hydropower is water power, geothermal power is a power that is generated by the internal heat of the Earth. It does not cost as much to create hydropower than it is to geothermal power. Hydropower costs: putting a machine down near a body of water. Geothermal power costs: digging a hole into the Earth and putting a machine. It costs about $20,000 to install the geothermal machine and about 3 cents per kW, it costs about $2,000 to install the hydraulic energy machine and about 80 cents per kW.