NEMA Publishes Standard Update for Electricity Meters

The National Electrical Manufacturers Association (NEMA) has published ANSI C12.20-2015 American National Standard for Electricity Meters—0.1, 0.2, and 0.5 Accuracy Classes. This revised standard establishes the physical aspects and acceptable performance criteria for 0.1, 0.2, and 0.5 accuracy class electricity meters meeting Blondel’s Theorem, and is used by meter manufacturers and electrical utilities to conduct performance tests of electricity meters for revenue purposes.

“ANSI C12.20-2015 is a significant update to the standard since its inception in 1998,” says Shannon Edwards, electronics engineer, NIST, Chair, ANSI C12 Subcommittee 1. “This document addresses the challenges of metering in the 21st-century environment.”

Enhancements in this fourth edition:


  • Creation of a 0.1 Accuracy Class improving available accuracies for ANSI devices by a factor of two
  • Inclusion of harmonic waveform testing to further ensure metering accuracy with distorted loads
  • Clarification that the standard only applies to applications where Blondel’s Theorem is met
  • Improvements in the definition of the Optical Test Output Port (OTOP)

ANSI C12.20-2015 is available in hard copy or as an electronic download on the NEMA website.

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