Electric Vehicle Fueling and Submetering: U.S. National Work Group

In July 2024, the U.S. National Work Group (USNWG) on Electric Vehicle Fueling and Submetering completed a major goal in establishing the method of sale, tolerances and other technical requirements, and related test procedures for commercial electric vehicle supply equipment (EVSE) in the NIST Handbooks and via adoption through the National Conference on Weights and Measures (NCWM).  Thus, NIST OWM does not plan to reconvene the USNWG. Rather, OWM plans to use its resources to develop a comprehensive EVSE metrology training program for our customers and stakeholders.  Developing and providing training is one of the final components to be realized in supporting the EVSE infrastructure across the U.S.  We will also continue to partner with NCWM to cooperatively develop outreach and training activities that will benefit all EVSE stakeholders.

What We Do 

The Electrical Energy U.S. National Work Group (USNWG) was formed in 2012 to develop proposed requirements for commercial electricity-measuring devices (including those used in sub-metering electricity at residential and business locations and those used to measure and sell electricity dispensed as a vehicle fuel) and to ensure that the prescribed methodologies and standards facilitate measurements that are traceable to the International System of Units (SI). In 2016, the USNWG agreed to modify its 2013 version of Operational Guidelines to restructure into two subgroups: (1) Electric Vehicle Fueling Equipment (EVFE) (aka Electric Vehicle Fueling Systems (EVFS), Electric Vehicle Supply Equipment (EVSE) or Electric Vehicle Chargers) and (2) Watthour Type Electric Meters (WHE). This work is not intended to address utility metering in the home or business where the electricity metered is consumed by the end purchaser and that falls under the authority of entities such as the local utility commission.

The Electric Vehicle Fueling and Submetering USNWG will review and propose changes as needed to:

1. Draft requirements for equipment used to measure and sell electricity in commercial applications for possible inclusion in NIST Handbook 44, ''Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices''; and
2. Draft procedures for type evaluation, laboratory, and field testing of equipment for possible inclusion in Examination Procedure Outlines (EPOs) and other procedure and technical guidance documents.

Meetings and Topics

The USNWG meeting topics include current and emerging device technologies used in commercial electric measuring systems related to: (1) Method-of-sale requirements; (2) metrology laboratory standards and test procedures; (3) uncertainties; (4) measurement traceability; (5) tolerances and other technical requirements for commercial measuring systems; (6) existing standards for testing equipment; (7) field implementation; (8) data analysis; (9) field test and type evaluation procedures; (10) field enforcement issues; (11) training at all levels; and (12) other relevant issues as identified.

The USNWG's technical output may result in the revision of current standards or the development of new standards for testing equipment, including documents such as the NIST Handbook 105 Series, Examination Procedure Outlines (EPOs), NIST Handbook 44, and NIST Handbook 130, as well as proposed changes to requirements and testing procedures for commercial devices and systems used to assess charges to consumers for electric vehicle fuel.

Of Further Interest

• New EPO 30 Retail Electric Vehicle Fueling Systems is now published (November 2024) and is based on the 2025 edition of NIST Handbook 44.
• The International Organization of Legal Metrology (OIML) Guide (G) 22 Electrical Vehicle Supply Equipment was published in September 2022 and is intended to address built-for-purpose systems that incorporate AC or DC energy metrology, whether that metrology is accomplished by using a separate type-approved meter or one that is integrated into the electronics of the EVSE. OIML G 22 does not apply to wireless charging systems. 
• The National Conference on Weights and Measures (NCWM) National Type Evaluation Program (NTEP) began accepting applications for Alternating Current (AC) EVSE systems on November 1, 2021.  NCWM Publication 14 Checklist for EVSE devices is based on NIST Handbook 44 Sections 1.10, 3.40, and 5.55.
• See our Electric Vehicle Fueling FAQs for more information.

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