Gas-fired power plant

A gas-fired power plant is a type of thermal power station that generates electricity by burning natural gas, which is mostly methane. These facilities supply roughly a quarter of the world’s electricity and are major contributors to greenhouse gas emissions. The process works by converting the chemical energy in the gas into heat, then into mechanical energy, and finally into electrical energy, though the conversion is limited by the Carnot cycle’s efficiency ceiling.

In energy planning, gas plants are often used for dispatchable power—filling gaps when variable renewables like wind and solar fall short, especially where hydropower or grid connections aren’t available. By the early 2020s, battery storage became competitive with gas peaker plants for this role. Some gas plants can burn other fuels like oil, coal, or hydrogen alongside natural gas, but most analysts doubt that existing gas turbines will be successfully converted to run on hydrogen, potentially stranding those assets.

Excess heat from the process can be captured in cogeneration plants to warm buildings, produce hot water, or heat industrial materials.

There are several types of gas-fired plants. Gas turbine plants use industrial turbines (heavier than aeronautical designs) that are tightly integrated with generators and heat recovery equipment. When waste heat from a gas turbine is captured by a heat recovery steam generator (HRSG) to run a steam turbine, the setup is called combined cycle (CCGT), achieving efficiencies up to 55% or higher—for instance, the General Electric 9HA reached 62.22% efficiency at 1,540 °C, and GE’s 826 MW HA model hit over 64% in 2018, with a target of 65% by the early 2020s. Aeroderivative turbines can also be used in combined cycles, though with slightly lower efficiency, and can be paired with cogeneration or inlet air cooling via absorption chillers.

Simple cycle (open-cycle) gas turbines are cheaper to build and can start very quickly, making them ideal as peaking plants that run only a few hours a day. They typically produce 100 to 400 MW with 35–40% efficiency.

CCGT plants usually pair two gas turbines with one steam turbine, costing slightly more than simple cycle but offering higher efficiency and dispatch times of about half an hour.

Steam turbine plants burn gas to fire boilers that produce steam for turbines. Built through the 20th century as coal alternatives, they lack quick-start capability and are much less efficient than combined cycle plants. Many older units are being retired in the U.S., but converting coal plants to gas burners can extend their life while cutting emissions.

Reciprocating internal combustion engines are much smaller—under 20 MW—and are used for emergency power or balancing variable renewables like wind and solar.

On greenhouse gas emissions, efficient CCGT plants emit about 450 grams of CO₂ per kilowatt-hour, roughly half that of coal but far more than nuclear or renewables. Less efficient simple-cycle turbines emit around 670 g/kWh, and some older gas turbines can match the highest coal emissions. Full life-cycle emissions are higher due to methane leaks from gas extraction and transport.