What Should You Charge for EV Charging? Per kWh, Per Hour, or Both

The energy price is a cost-recovery instrument. Its floor is your own volumetric rate plus the share of demand charge, network subscription, processing and maintenance that the session should carry. Set it below that and every session loses money faster the better the site performs.The time price is a scarcity instrument. It has nothing to do with what the electricity cost and everything to do with what the parking space is worth to you and to the next driver. On a site where stalls are abundant it can be zero. On a site where they are contested it is the only thing that keeps a charging stall from becoming a long-stay parking space with a plug in it.Confusing the two is how sites end up with a price that is simultaneously too high for a driver topping up for twenty minutes and too low to move a finished car out of the stall. Charge separately for the energy and for the time and both problems go away.

When you sell electricity by the kilowatt-hour you are selling a measured quantity of a commodity, and that is regulated in the United States the same way a gasoline pump or a supermarket scale is regulated. The relevant standard is NIST Handbook 44, which contains a section specifically for electric vehicle fuelling systems covering measurement accuracy, what the display must show and what the receipt must contain.Most states adopt Handbook 44 by reference into their own weights-and-measures law, and enforcement is typically run by a state department of agriculture or a state weights-and-measures office. What varies, and varies a lot, is the date a given state began applying the electric vehicle section, whether it requires equipment to hold a national type-evaluation certificate, whether devices must be registered and periodically inspected, and how the rules apply to equipment installed before the requirement took effect.The practical consequence is a hardware constraint. If your state enforces it, a charger you intend to sell energy from has to be the right device, and finding that out after the pedestals are set is an expensive way to learn it. Call your state office before you sign a hardware order, and ask the vendor in writing whether the specific model carries the certification your state requires.

Charging by the minute or by the hour is not a sale of a measured quantity of electricity, which is the reason some operators use it in jurisdictions where the device requirements are onerous. Do not treat that as settled advice for your state — confirm it with your own weights-and-measures office, because states differ and the analysis is theirs to make, not ours.Time pricing has a real fairness problem regardless of the law. A vehicle that accepts 11.5 kilowatts and a vehicle that accepts 6.6 kilowatts pay the same for the same hour and receive very different amounts of energy. Drivers notice this quickly and it generates complaints, particularly in a residential setting where the same people use the same stalls every night.The arrangement that avoids both problems on a lot of sites is a modest hourly rate for the connected period plus a materially higher idle rate once charging completes. It recovers the stall, it is easy to explain on a sign, and it does not require you to defend a per-kilowatt-hour meter reading to anyone.

If you are pricing by energy, do the floor calculation before you look at what anyone else charges. Start with your volumetric energy rate from the utility bill — the commercial rate, not a residential or national figure. Add the demand contribution: your tariff's demand rate multiplied by the kilowatts the chargers add to the monthly peak, divided by the kilowatt-hours you expect to sell in the month. Add the per-port subscription and the maintenance reserve on the same per-kilowatt-hour basis. Add payment processing, remembering it has a fixed component per transaction.That sum is the price at which you break even at your assumed volume. Below it, every session is subsidised. Above it, you have a margin — and the margin has to be big enough to absorb the fact that your volume assumption is probably optimistic.Two things distort this calculation constantly. The first is using the wrong energy rate, usually a residential one. The second is omitting the demand term, which on a demand-billed tariff is regularly larger than the energy cost itself and does not shrink when the port is quiet.

Whatever you decide, post it at the stall in a form a driver can read before plugging in: the energy rate, the time rate, when the idle fee starts and what it is, and any session fee. Most disputes in commercial charging are disclosure disputes rather than price disputes. A driver who knew about the idle fee pays it; a driver who discovers it on a receipt calls the leasing office.Where you have residents rather than visitors, the disclosure requirement is stronger and often contractual. Billing a resident for electricity — as opposed to billing a visitor for a charging service — can bring landlord-tenant rules and, in some states, utility-resale rules into play. That question is covered separately in the multifamily cluster and is worth reading before you set a resident price.Finally, decide up front how the price changes. Tariffs move, and a price you set once and never revisit turns into a subsidy the year your utility restructures its rate. Put a review date in the operating plan.