Monitoring Insights

EPA collects continuously monitored emissions data from electricity generating units (EGUs) to assess compliance with a variety of federal air quality programs. These emissions and related data comprise EPA’s Power Sector Emissions Data. CAPD regularly analyzes the data to resolve questions, identify monitoring trends, and discover monitoring insights. CAPD periodically posts these short analyses to share these monitoring insights.

• Monitoring Methods Analysis (pdf) (188.46 KB, January 3, 2024)

  This analysis shows the utilization of monitoring methods using 2021 emissions data. The analysis finds that a significant majority of emissions are monitored using the most accurate and quality assured method.

• Alternate Performance Specifications for Relative Accuracy Test Audits (pdf) (687.25 KB, November 7, 2022)

  This analysis evaluates relative accuracy test audits (RATAs) passed using the alternate performance specifications between 2010 and 2021. This analysis finds that reported mean differences are significantly lower than required and the usage of alternate performance specifications has increased over the past 11 years.

• Relative accuracy (RA) in EPA CAMD's Power Sector Emissions Data (pdf) (181.1 KB, May 10, 2022)

  This analysis evaluates relative accuracy test audit results between 2017 and 2021 to assess the performance of the part 75 monitoring systems. This analysis finds that reported RA values are lower than required and that RA values are either constant or improving over the past five years.

• Percent monitor data availability in EPA CAMD's Power Sector Emissions Data (pdf) (125.28 KB, July 22, 2021)

  This analysis evaluates the reliability of continuous emission monitoring systems (CEMS) for the part 75 emission monitoring program between 2015 and 2020. The analysis finds that a significant majority of CEMS are providing valid, quality assured data for more than 99 percent of operating hours.

• Substitute data in EPA CAPD's Power Sector Emissions Data (pdf) (144.22 KB, February 16, 2021)

  This analysis explores the use of measured and substitute data in the Power Sector Emissions Data between 2015 and 2019. The analysis finds that substitute data represents a minor portion of the total reported data.

• Fundamentals of Successful Monitoring, Reporting, and Verification under a Cap and Trade Program (pdf) (167.06 KB, November 2006)

  This paper explores the elements of an emission monitoring and reporting program that contribute to the success of emission trading programs. The paper uses part 75 as a case study.