Natural Gas Generation: The Technology Matters

Natural gas can be converted to electricity using several different technologies, and their efficiency differs substantially.

EIA's 2024 average tested heat rates for natural-gas generators were 7,548 Btu/kWh for combined-cycle units, 8,924 Btu/kWh for internal-combustion generators and 10,999 Btu/kWh for gas turbines. Heat rate measures the amount of fuel energy required to produce a unit of electricity, so lower is more efficient.

Those averages correspond to approximate electric efficiencies of 45%, 38% and 31%, respectively. Put another way, EIA's tested averages imply that a simple-cycle gas turbine requires about 46% more natural-gas energy per kWh than combined cycle, while an internal-combustion generator requires about 18% more.

Combined-cycle plants improve efficiency by capturing hot turbine exhaust and using it to produce additional electricity. Reciprocating engines offer modularity and can be deployed as multiple units. Simple-cycle gas turbines are flexible and can start rapidly, but their lower efficiency means more fuel is required for the same electrical output.

Fuel use is only one dimension. EPA regulates stationary combustion turbines and reciprocating engines because combustion also produces pollutants such as nitrogen oxides, carbon monoxide, volatile organic compounds, and hazardous air pollutants. Actual emissions depend on technology, operating conditions, and pollution controls, so universal emissions-per-MWh numbers should not be applied across all gas-generation configurations.