The average operating heat rate for combined-cycle generators has declined over the last five years. According to the EIA, natural gas combined-cycle power generators installed since 2015 have an average heat rate of 6,654 Btu/kWh. This average is nearly 25% lower than units installed before 2000, which have an average operating heat rate of 8,840 Btu/kWh.
Efficiencies have largely been the result of turbine and steam generator advancements. The improvements have put older generators at an economic disadvantage due to higher operating expenses when compared to newer generators. As a result, newer generators have higher capacity factors as they are dispatched more frequently.