EV Charging Pricing: kWh Rates and Lawful Time Fees

There Is Only One Lawful Method of Sale

Most guidance for fuel retailers presents EV charging as a choice between three pricing models — by the kilowatt-hour, by the minute, or a flat fee per session — and invites you to pick one. That framing is wrong, and acting on it creates weights and measures exposure rather than avoiding it.

The NIST Office of Weights and Measures states the position plainly: electricity sold as a vehicle fuel may be sold only by the kilowatt-hour, and an EVSE may not sell electricity as a vehicle fuel by units of time. NIST Handbook 130, Section 2.33, makes the kilowatt-hour the official unit of measure and requires a unit price expressed per kWh. NIST Handbook 44, Section 3.40 (Electric Vehicle Fueling Systems), added as a tentative code in 2015 and permanent on the first of January, 2023, requires the device itself to indicate and record the energy delivered in kWh.

So the real decision is not which of three models to use. It is how to set a defensible $/kWh price, and how to add a time-based charge in the one form the rules permit — as a separate, disclosed fee for occupying the space, not as a price for the electricity. That is what the rest of this article covers.

One consequence up front: per-minute billing does not avoid a metering obligation, and a flat session fee is not a way around the unit price requirement. Both are commonly recommended as compliance shortcuts. Neither is one.

What the Device Has to Do

Section 3.40 is short, free to read on nist.gov, and worth reading in full before you sign a hardware order. Its core obligations for a retail EVSE:

• Indicate and record in kWh. The device must show the energy delivered and record it, and it must be of the computing type — showing energy delivered, the unit price and the total price for the transaction.
• Display the unit price on each face of the device, so a customer can see the $/kWh before starting.
• Issue a receipt carrying the same detail as the display.
• Hold accuracy tolerances. AC systems: 1.0 percent acceptance and 2.0 percent maintenance. DC systems: the same 1.0 and 2.0 percent, except that a DC system placed in service before January 1, 2025 and marked Class 5 keeps a 5.0 percent tolerance until that provision expires on January 1, 2034, and all DC EVSE placed in service before January 1, 2025 are exempt from the tolerance requirement until January 1, 2028.
• Be type-evaluated. The National Type Evaluation Program will type-evaluate only EVSE that comply with the code and carry safety certification from a nationally recognized testing laboratory. California runs its own California Type Evaluation Program.

Handbook 44 is published by NIST; its EV fueling requirements were developed by the U.S. National Work Group for Electric Vehicle Fueling and Submetering and adopted through the National Conference on Weights and Measures, which also administers the National Type Evaluation Program. It binds you only where your state has adopted it, and adoption dates, enforcement dates and penalties are set state by state under each state’s own weights and measures statute. There is no national penalty schedule for EV charging price violations; any figure presented as one is invented.

The practical step: ask your supplier for the type approval certificate covering the exact model and firmware, and confirm your state recognises it. A charger that meets the electrical code but has not been type-evaluated is not a lawful retail measuring device, and finding that out after installation is expensive. Weigh this alongside power rating in our charger hardware comparison.

Time Charges, Done Lawfully

Time still has a legitimate place in your price structure. What it cannot do is price the electricity. What it can do is price the space.

A separate, properly disclosed fee for the time a vehicle occupies the bay — parking, or an overstay after charging completes — is permitted, and the timing element measuring it falls under Handbook 44 Section 5.55, Timing Devices. This is the mechanism behind what networks call an idle fee, and it is useful to a fuel retailer: it turns bay turnover from a courtesy into a financial incentive, as a pay-and-display parking system does.

Structured correctly, a retail charging transaction therefore has two components:

1. A $/kWh unit price for the energy delivered, indicated and recorded by the EVSE.
2. An optional time-based occupancy or overstay fee, disclosed separately, with its own unit price per unit of time.

Where an EVSE applies more than one unit price in a transaction, or adds a time-based fee, Section 3.40 requires it to indicate the start and stop time, the energy delivered, the unit price and the total for each phase, plus the total time measured, the unit price for the time-based service and the total transaction price — and to put the same detail on the receipt. Confirm with your network provider that your structure can be configured and displayed and printed that way; a platform can often bill a fee it cannot properly display, and the display is part of the requirement.

Two things that follow from this and are easy to get wrong. Charging the idle fee while the vehicle is still actively drawing power blurs the line between an occupancy fee and a time price for energy; keep the trigger unambiguous and disclosed. And a session cap or bundled offer has to sit on top of a kWh unit price rather than replacing it — a flat fee that is the entire price of the energy does not satisfy the unit price requirement, so confirm any bundled promotion with your state weights and measures authority before launching it.

Building the $/kWh Number

There is no published retail charging rate to copy and no defensible multiple of your cost to apply. Build the number from four inputs, all of which you can obtain.

1. Your delivered electricity cost. Pull your actual commercial tariff, including demand charges, and work out the effective cost per kWh delivered at your expected utilization — not the energy rate alone. At a low-utilization DC site the demand charge can dominate, because it is set by your peak kW regardless of how many sessions you ran. For scale only, EIA put the U.S. average retail price of electricity to commercial customers at 14.19 cents per kWh in June 2026, and to residential customers at 18.34 cents per kWh in the same month. Your tariff is what governs; the residential figure matters only because it is the benchmark your customer is implicitly comparing against.
2. Network fees. Networks charge either a revenue share or a per-port or per-session fee. None publishes commercial terms, so get yours quoted in writing with the term and the renewal price, and put the actual number into the margin calculation rather than an assumed percentage.
3. Hardware and installation amortization. Get installed cost quoted for your specific site. The swing factor is utility service, transformer and trenching work, not the charger sticker price. Amortize the quoted figure over the equipment life and divide by projected annual sessions. Our installation cost guide lists the scope items that get left out of early estimates.
4. Local competitive rates. Read the posted $/kWh at chargers in your trade area, which is public information displayed on each device. That, not a national average, is the price your customer compares you to.

Then check the result as you would a fuel price: does the margin per kWh, at a utilization you can defend from your own traffic data, cover network fees, amortization and service? If not, the answer is not a higher rate that sends customers elsewhere — it is that the site does not support the deployment yet. Our charging ROI method walks the full calculation.

Revisit the rate on a schedule. Utility tariffs change at rate cases, competing chargers open, and utilization moves; a rate set once and left is the same mistake as a fuel price set once and left.

Where Your State Stands

EV charging sits at an unusual intersection of utility regulation, consumer protection and weights and measures enforcement, and the enforcing agency is not the same one everywhere. Three examples show the range:

• California. The CDFA Division of Measurement Standards treats commercial EVSE as commercial measuring devices requiring type approval through the California or National Type Evaluation Program. New commercial AC EVSE installed on or after January 1, 2021 are fully subject to the regulation, with AC units installed earlier required to comply by January 1, 2031. New commercial DC fast chargers installed on or after January 1, 2023 are subject, with earlier DCFC required to comply by January 1, 2033.
• Colorado. The Division of Oil and Public Safety, within the Department of Labor and Employment, finalised Colorado’s first comprehensive retail EVSE regulations following HB25-1267, taking effect July 1, 2026 and treating EV chargers as retail fueling points subject to weights and measures accuracy standards. The regulator is OPS, not the Department of Agriculture.
• Texas. Senate Bill 1001 (88th Legislature, 2023) created a registration and inspection regime now sitting at Texas Occupations Code Chapter 2311 and 16 Texas Administrative Code Chapter 96, with administrative penalties. The Texas Department of Licensing and Regulation registers electric vehicle supply equipment and inspects and tests it. Texas is not a permissive market for EV charger metering.

The lesson is to find out which agency holds the file in your state before you activate billing, because it is an agriculture department in some states and a labour or licensing agency in others. Ask that agency two questions in writing: has the state adopted Handbook 44 Section 3.40, and what type evaluation will you accept? The same discipline applies here as to your dispensers — see our weights and measures compliance guide.

Pricing and the Store Inside

Your charger is a traffic driver for the store, and the price structure changes how long people stay. A DC fast charging session on a modern EV typically runs 15 to 45 minutes — long enough for coffee, a snack and the restroom, which is precisely the advantage a fuel retailer has over a parking-lot charger.

An aggressive idle fee protects turnover but creates clock anxiety, and a customer watching the clock stays in the car. Set the occupancy fee so it bites only after charging completes, disclose it clearly when the session starts, and leave the charging period relaxed. Beyond that:

• Offer a per-session discount redeemable as in-store credit rather than as a lower energy price — it moves the incentive inside the building without disturbing the unit price on the device.
• Integrate charging with your loyalty programme so repeat visits earn across fuel, store and charging.
• Site slower AC equipment away from the fast-charge bays. It anchors longer visits without congesting the positions that turn over.

Measure the effect rather than assuming it. Compare inside sales during charging sessions against your baseline once the chargers are live, and let that measurement, not a borrowed uplift figure, decide how much you give away on the charging side.

What to Do Next

1. Confirm your state’s adoption and enforcing agency in writing before activating billing.
2. Get the type approval certificate for the exact model and firmware, and check it against your state’s accepted programme.
3. Calculate your effective delivered cost per kWh from your own tariff, including demand charges, at a defensible utilization.
4. Review your network contract for rate-setting flexibility, revenue share, and whether the platform can display and print a two-component transaction.
5. Set the occupancy fee separately from the energy price, with an unambiguous trigger and clear disclosure.
6. Re-price on a schedule as tariffs, utilization and local competition move.

The compliance question and the pricing question are the same question here. Get the method of sale right and the rest is ordinary retail arithmetic; get it wrong and the rate you chose is the least of your problems.

Sources

Checked against these primary sources on 2026-09-08. Unlinked sources are cited by name because this site links only to a restricted set of hosts.

• NIST Office of Weights and Measures, Electric Vehicle Fueling FAQs — method of sale; electricity may not be sold by units of time
• NIST Handbook 44, Section 3.40 — Electric Vehicle Fueling Systems
• EIA, Electric Power Monthly — average retail electricity price by sector
• Texas Department of Licensing and Regulation — EV charging station laws and rules
• NIST Handbook 130, Section 2.33 — method of sale for electricity as a vehicle fuel
• CDFA Division of Measurement Standards — Zero Emission Vehicle Projects (EVSE compliance dates)
• Colorado Division of Oil and Public Safety — retail EV charging standards under HB25-1267