Quarter of U.S. power plants can start up within hour

A quarter of power plant operators can be up and fully running from a complete shutoff, according to an annual survey of electricity generators from the Energy Information Agency. Gas turbines are relatively fast to start up.

Natural gas combined-cycle plants account for more generating capacity than any other generating technology in the U.S. Most of those systems can reach full operations in between one to 12 hours. Some can start up within an hour. Plants that take over 12 hours to start up are increasingly rare: only 4% of new generating capacity from 2010 to 2019 requires more than half a day to reach full load.

Electricity-generating technologies vary in startup time due to differences in processes, especially cold shut downs. A generator’s ramp rate, on the other hand, reflects how quickly that generator can modify its power output once it’s operating. Coal and nuclear fuel (12-hour startup time) have higher startup times - sometimes more than half a day - to reach full operation. Steam turbines are a bit slower to form steam, which has to reach certain temperature, pressure, and moisture content thresholds before it can be used in the steam turbine. Most hydroelectric turbines can go from cold start to full operations in less than 10 minutes.