[deport]

A combined-cycle power plant uses both a gas and a steam turbine
together to produce up to 50 percent more electricity from the same
fuel than a traditional simple-cycle plant. The waste heat from the
gas turbine is routed to the nearby steam turbine, which generates
extra power.

[Presbyterian Reporter]

So both types of plants require natural gas as the feedstock. Am I correct?

[WhoisAlanGreenspan?]

Yep. At one of my past jobs we installed a co-gen unit. It was fueled by natural gas I don't remember the output, but it made both electrical power and steam in such savings that the investment paid for itself in 5 years.