Updating Thermal Power Plant Efficiency Measures and Operational Characteristics for Production Cost Modeling

This report describes a method to estimate heat rates and operating ranges for thermal power plants, such as natural gas power plants. The heat rate of a power plant measures the amount of fuel used to generate one unit of electricity. Power plants with lower heat rates are more efficient than plants with higher heat rates. Heat rates are key inputs in production cost models. Production cost models simulate electric systems to estimate electricity production, cost, fuel consumption, reliability, and emissions.

This method uses hourly fuel consumption and electricity generation data, from public sources, for different power plants. The method finds the operating range of each power plant using hourly generation data and plant capacities. Then California Energy Commission staff analyzes the relationship between fuel use and electricity production to create trend lines of the heat rate. Finally, the method uses several points on the trend line to estimate the heat rate of the power plant in the associated operating range.

Based on the method results, staff changed the minimum operating level from 25 percent for all power plants to different levels depending on plant type. Staff found that the updated heat rates and operating ranges align well with recent power plant operations compared to the old values.

Staff recommends making periodic updates to power plant heat rates and operating ranges. These updates are important as increased renewable generation and other policy goals will affect the operation and efficiency of thermal power plants. To improve this method in future updates, staff also recommends using subhourly fuel use and generation, along with estimates of station service using public data.