EV charging metrology is the science and regulation of accurately measuring the electricity delivered to vehicles, so that drivers are charged fairly when energy is sold by the kilowatt-hour.
Selling electricity by the kWh makes a charger a commercial measuring device, like a gas pump or a deli scale. In the United States, requirements for EV fueling systems are published in NIST Handbook 44, and states adopt and enforce them through their weights and measures programs. California has been among the most active, requiring certified equipment and field testing.
What it covers
- Accuracy. Limits on how far measured energy may differ from energy actually delivered.
- Type approval. Equipment models evaluated and certified before commercial use.
- Display and receipts. Price, energy delivered and total cost shown to the driver.
- Field testing. Inspection of installed chargers by state or local officials.
Why it matters to owners
Equipment that is not certified may not be legally used to sell energy by the kWh in some states, which can force time-based pricing instead. Confirm certification before buying. See kW versus kWh.
The Parkonomics view
If drivers pay for energy, the meter is part of the product. Certified measurement protects customers and keeps the charger legally able to sell what it delivers.
Related terms: kW versus kWh, EVSE, Charger, EV Ready