This note uses electricity generator level 2001–2018 US capacity, generation, and heat input data to evaluate trends in same-plant capacity factor (how much plants run) and heat rate (how efficiently plants run) as plants age. Based on compound annual growth rates for capacity factor and, for thermal plants, heat rate, and based on the subset of US plants that have been operating since 2010 or earlier, same-plant capacity factors increased slightly, and heat rates decreased slightly, between 2001–2018 (weighted average based on 2018 plant capacity). Trends vary by region, fuel, and plant age. Notably, US natural gas-fired power plants tended to run more, and more efficiently, as they aged, while coal-fired power plants tended to run less, and less efficiently. Potential drivers include relative plant age, policy, financial competitiveness, and an anticipated tendency for plant operators to react to the effects of equipment aging with maintenance, repair, replacement, and optimization. These observations can inform committed emissions-based research, which requires making assumptions about how plant operational characteristics change (or do not) as they age.

本说明使用 2001 年至 2018 年美国发电量、发电量和热输入数据来评估同一电厂容量因子（电厂运行量）和热耗率（电厂运行效率）随着电厂老化的趋势。根据容量因子的复合年增长率和热电厂的热耗率，以及自 2010 年或更早开始运营的美国电厂的子集，同厂容量因子略有增加，热耗率略有下降，介于2001-2018 年（基于 2018 年工厂产能的加权平均值）。趋势因地区、燃料和植物年龄而异。值得注意的是，随着老化，美国的天然气发电厂往往运行得更多、效率更高，而燃煤发电厂的运行速度往往更少、效率也更低。潜在驱动因素包括相对厂龄、政策、金融竞争力、以及工厂操作员通过维护、修理、更换和优化对设备老化的影响做出反应的预期趋势。这些观察可以为承诺的基于排放的研究提供信息，这需要对工厂运行特征如何随着年龄的变化（或不）做出假设。