[org.whodat]

And what does the most plants use, steam, boiling water.

[thackney]

And what does the most plants use

Most Natural Gas plants are combustion turbines. They may use steam or hot water as secondary waste heat recovery. These combined cycle power plants with a primary combustion turbine are more efficient than a straight steam turbine power plant.

Development of High Efficiency
Gas Turbine Combined Cycle
Power Plant
http://www.mhi.co.jp/technology/review/pdf/e451/e451015.pdf

[thackney]

To help understand high efficiency combined cycle power generation:

Smaller peaker plants used to cycle on and off as load changes or other power plants trip off-line are typically straight combustion turbine without the steam section.