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Auditor accuracy testing reconfirms ‘revenue grade’ equivalency

by Murray Hogarth
posted on Monday, October 1st, 2018


Recently, the Wattwatchers Auditor 6M 6-channel energy meter was evaluated for accuracy through professional laboratory testing.

The test equipment was the same as that typically used for evaluating National Measurement Institute (NMI) pattern-approved meters* for electricity billing purposes.

The results of the evaluation are that:

  • Auditors are linear over a range exceeding 1000:1 to better than 0.1%
  • The Auditors under test were accurately calibrated
  • In conjunction with the CT’s supplied by Wattwatchers, Auditor accuracy meets the requirements of NMI* M6 as called out by IEC62053-21 as a Class 1 instrument.

These results are documented in a detailed test report, available on request from Wattwatchers via

The results apply to all variants of the Auditor series of products including:

  • Auditor 6M (cellular, monitoring-only)
  • Auditor 6M/3SW (cellular, monitoring + switching)
  • Auditor 6M+One (cellular, monitoring + switching, ModBus-enabled, bundled with NMI pattern-approved second meter)
  • Auditor 6W (WiFi, monitoring-only)
  • Auditor 6W/3SW (WiFi, monitoring + switching)

*NOTE: Auditor devices are not currently NMI pattern-approved, but this testing update demonstrates that they are ‘Class 1’ accurate (min. +/- 1%) and are equivalent to ‘revenue grade’ in terms of having the same or superior accuracy to typical pattern-approved meters. In September 2018, Wattwatchers announced a new product line which bundles compact, NMI pattern-approved single- and three-phase interval meters with an Auditor 6M. READ MORE