Steam turbines are one of the most versatile and oldest prime mover technologies still in general production and used to drive a generator or mechanical machinery. As noted above, steam turbine power generation has been in use for about 100 years, when the turbines replaced reciprocating steam engines due to their higher efficiencies and lower costs. Most of the electricity produced in the United States today is generated by conventional steam turbine power plants. The capacity of steam turbines can range from 50 kW to several hundred megawatts for large utility power plants. Steam turbines are widely used for combined heat and power (CHP) applications in the United States and Europe.