The average cost to build a geothermal power plant is $2,000-$5,000 per kWh. With an "average" plant size of 38 MW, you could expect to pay about $2,000-$2,500 or $7.6-9.8 million. The smaller the plant, the more costs per kWh will be. For example, costs for a 1 mWh plant are estimated at around $5,000 per kWh.