The U.S. Geological Survey (USGS) developed models to estimate the amount of water that is withdrawn and consumed by thermoelectric power plants (Diehl and others, 2013; Diehl and Harris, 2014; Harris and Diehl, 2019). The thermoelectric water use models are based on linked heat-and-water budgets that are constrained by power plant generation and cooling system technologies, the amount of fuels consumed and electricity generated, and environmental variables. The heat-budget side of the models calculates the amount of waste heat (fuel heat that is not converted to electricity) that is removed from the steam used to drive the turbines that generate electricity and transferred to the cooling system in a thermoelectric power plant’s condenser, which is defined as the condenser duty (Diehl and others, 2013). Condenser duty is an intermediate calculation and an input to the water-budget side of the thermoelectric water use models that estimates plant-specific water withdrawal and consumption. The models provide consistent methods for water-use estimation across U.S. thermoelectric plants and estimates independent of plant operator-reported data. This dataset presents a historical reanalysis of monthly condenser duty estimates from 2008 to 2020, and associated information for 1360 water-using, utility-scale thermoelectric power plants in the conterminous United States operational within the time period. These monthly condenser duty estimates were input to the water-budget side of the thermoelectric water-use models for the 2008-2020 historical reanalysis of water withdrawals and consumption by HUC12, month, and year for the conterminous United States (Galanter and others, 2023).