Which best contrasts hydroelectric power and geothermal energy? Turbines are used in power plants that harness only geothermal energy but not hydroelectric power. Turbines are used in power plants that produce hydroelectric power but not geothermal energy. In the US, geothermal energy is a more widely used energy source than hydroelectric power. In the US, hydroelectric power is a more widely used energy source than geothermal energy.