Electric Vehicle Fueling FAQs

Also referred to as Electric Vehicle Supply Equipment (EVSE), electric vehicle fueling systems vary considerably in both performance and design. Some are capable of fully charging an EV battery over several hours (AC Level 2) while others can provide full charge in well under an hour (Level 3, i.e., “DC Fast-Chargers"). Widely used commercial fueling systems are rated to deliver power levels in the range of approximately 22 kW to more than 350 kW. Several charging standard connectors are used throughout the U.S., including the Combined Charging System connectors (CCS1 and CCS2), the North American Charging Standard (NACS) and SAE J1772 (“J plug”).

The U.S. Department of Energy's Alternative Fuels Data Center provides further information regarding EV Charging Infrastructure. 

If you have a complaint and/or inquiry, you may contact your State Weights and Measures program for assistance. Please see the list of State Directors for more information. 

You may also directly contact the business and/or operator responsible for the EV charging station. Most public EV chargers have a customer service number and/or 24/7 online support available. 

Consistent methods of sale (such as $/kWh) that are based on the amount of energy actually delivered to an EV helps ensure that consumers can make equitable price and value comparisons across various station locations and/or charger levels.

Yes. At present, a variety of methods for energy pricing via EV charging services can be found within every state, and some are based on quite different measurement units. For example, energy pricing structures can range from $/kWh to $/time connected (min, hour), flat fees for individual connection sessions, and may include additional fees for parking or membership.

Please see Section 3.2 of NIST SP2200-03 An Evolving Regulatory Landscape for Commercial Electric Vehicle Fueling for more information.

NIST Handbook 44 requirements form the basis for type evaluation under the National Type Evaluation Program and for routine inspection and test procedures for measuring equipment for commercial electric vehicle refueling systems. Specifically, NIST Handbook 44 Section 1.10 General Code and Section 3.40 Electric Vehicle Fueling Systems Code provide specifications, tolerances, and other technical requirements for hydrogen measuring devices.

Section 3.40. Electric Vehicle-Fueling Systems of NIST Handbook 44 was added as a “tentative code” in 2015. In July 2022, the status of the code was changed from “tentative” to “permanent” effective January 1, 2023.

NIST Handbook 130 requirements in IV. Uniform Regulations - B. Uniform Regulation for the Method of Sale of Commodities Section 2.34 Retail Sales of Electricity Sold as Vehicle Fuel specifies the unit of kilowatt-hour (kWh) as the unit of measurement for sales of electricity as fuel and for related labeling and advertising requirements.

Based on NIST Handbook 44 (2024) code, the acceptance tolerance and maintenance tolerances for Electric Vehicle Supply Equipment (EVSEs) load tests are 1 % and 2 %, respectively. 

Note that all "fast charging" direct current (DC) based EVSEs (i.e., Level 3 fast chargers) are exempt from this requirement until January 1, 2028.

The legal metrology requirements in the NIST Handbooks 44 and 130 were developed by the U.S. National Work Group (USNWG) for Electric Vehicle Fueling and Submetering. The USNWG was formed in 2012 to develop requirements for commercial electricity-measuring devices (i.e., residential sub-metering, electric vehicle dispensers) to ensure that the prescribed methodologies and standards facilitate measurements that are traceable to the International System of Units (SI). This group is comprised of stakeholders from private industries, standards organizations, and state and federal government. The recommendations developed by the USNWG adhered to the weights and measures standards development process through the National Conference on Weights and Measures (NCWM) and for inclusion in the NIST Handbooks 44 and 130.