Gas Turbine Heat Rate & Thermal Efficiency Calculator
Calculate net heat rate (BTU/kWh & kJ/kWh), thermal efficiency on LHV and HHV bases, fuel gas consumption, and ambient temperature/elevation derating per ASME PTC 22.
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Ambient Operating Site Conditions
Heat Rate & Actual Site Output
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Frequently Asked Questions
What is the difference between LHV and HHV heat rate?
Lower Heating Value (LHV) assumes water formed during hydrocarbon combustion leaves as vapor (latent heat not recovered), which is the standard baseline used worldwide by gas turbine manufacturers. Higher Heating Value (HHV) includes the latent heat of water condensation and is typically 10% to 11% higher than LHV for natural gas.
Why does high ambient air temperature degrade gas turbine power?
A gas turbine is fundamentally a constant volumetric flow machine. When ambient air temperature rises, air density decreases, meaning the compressor ingests fewer pounds of oxygen per second. With reduced mass flow through the turbine expander, gross shaft power output drops by approximately 0.35% to 0.45% per °F.
What are typical heat rates for modern aeroderivative vs heavy-frame gas turbines?
Modern simple-cycle aeroderivative gas turbines (e.g. GE LM6000 or LMS100) achieve LHV heat rates of 7,800 to 8,500 BTU/kWh (40% to 44% efficiency). Heavy-duty F- and H-class industrial gas turbines in simple cycle operate around 8,500 to 9,200 BTU/kWh, but in combined cycle with an HRSG, heat rates plunge to an exceptional 5,400 to 5,800 BTU/kWh (60%+ efficiency).