Measurement and Price Transparency for Electric Vehicle Charging

When consumers go to use an electric vehicle (EV) charging station, they need to be confident that they’re getting the energy they pay for. The system of policies, requirements, and controls used to ensure fairness and consistency in the measurements used to charge a customer for a commodity such as electricity is called legal metrology. These principles are the same as those used in measurements for other traded commodities such as the weight of produce in the grocery store or the volume of gasoline delivered by a gas pump.

The Joint Office of Energy and Transportation (Joint Office) works in collaboration with the National Institute of Standards and Technology’s (NIST’s) Office of Weights and Measures to help states develop metrology and certification practices for charging at public EV charging stations and to train their certification and permitting teams to ensure chargers are reliable and compliant throughout the life of the equipment

Creating Consistent EV Charging Systems With Measurement Standards

While there are many different manufacturers and types of electric vehicle supply equipment (EVSE) and a variety of EVs with different charging needs, there must be consistency in the measurement of delivered energy across all equipment types and charging modalities. Establishing a legal metrology standard for EV charging would ensure that consumers can compare prices across station locations, charger levels, and different charging times.

This legal metrology standard is in NIST Handbooks 44 and 130 and has been voluntarily adopted by all states and territories.

Read NIST’s EVSE Program page for more information.

Improving Charging Station Reliability With EVSE Metrology Standards

The national EVSE site inspection standards set the foundation for consumers to have confidence that the chargers installed have been inspected to meet metrology standards. Site inspection standards also help state and local weights and measures officials make sure charging stations are operating effectively and meeting standards when installed and on an ongoing basis. State and local officials will implement these standards at their discretion beginning in January 2025, such as inspecting for permitting, price consistency, site safety, advertising, taxation, operation, and maintenance.

For consumers, this means you might start to see state officials marking EVSE with a label indicating that a successful inspection has occurred and the equipment’s next date for inspection. This also could mean that stations are temporarily taken out of service that don’t meet the requirements while a technician is routed to make necessary repairs.

Building an EVSE Maintenance Workforce With Training

To create an effective EV charging ecosystem and reliable customer experience, EVSE infrastructure must be both deployed and maintained. Working with the Office of Weights and Measures, the Joint Office is developing an EVSE metrology training curriculum to train more EVSE maintenance and operations technicians—both within state and local governments and the broader U.S. EVSE industry.

This program is designed for weights and measures officials, registered service agents, EVSE engineers, technicians, and manufacturers. It is in development for launch in 2025; to express interest in participating, please send an email with your contact information to owm@nist.gov.

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