EVSE Metering & Weights-and-Measures Rules
If you sell charging by the kWh, you may be operating a commercial measuring device in your state's eyes — the same legal category as a gas pump. Whether that triggers registration, inspection, and metering-accuracy requirements depends entirely on your state's adoption of the NIST Handbook 44 EVSE code.
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- Standing requirement
- When it applies
- Selling electricity to the public by the kWh in states that have adopted NIST Handbook 44's EV fueling systems code — adoption and enforcement vary by state.
- Whose obligation
- The charging station operator (device registration, inspection, pricing display); equipment metering capability determines whether compliance is possible.
- ZEF's status
- Requirements vary by state — see your state's page for whether and how its weights-and-measures program covers EVSE, and contact ZEF for metering specifications for your jurisdiction.
The Handbook 44 framework
NIST Handbook 44, maintained with the NIST Office of Weights and Measures, includes a code for electric vehicle fueling systems covering metering accuracy, pricing display, and device requirements for charging sold by energy delivered. Handbook 44 has no force of its own — it binds only as adopted by each state's weights-and-measures law, and states vary widely: some fully enforce the EVSE code with device registration and field inspection, some have adopted it but phased enforcement, and some have not extended their programs to EVSE at all.
What operators should check
Before launching kWh-priced public charging, check three things with your state's weights-and-measures authority: whether the EVSE code is adopted and enforced, whether devices must be registered or permitted, and what pricing-display rules apply. This site's state pages record each state's posture where it has been verified. Because this is a standing requirement, it applies to grant-funded and privately funded stations alike.
Frequently asked questions
Do weights-and-measures rules apply to free charging?
Generally these rules attach to charging sold by measured quantity (kWh). Free charging, and in some states time-based pricing, sits outside the metering-accuracy regime — but confirm with your state's weights-and-measures authority, since treatment varies.
Is there one national metering rule for EV chargers?
No. NIST Handbook 44 provides the model code, but it only applies as each state adopts and enforces it. The same charger and pricing model can face device registration and inspection in one state and no EVSE-specific requirements in the next.
Not sure what applies? Ask.
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