What it costs to charge an electric fleet per mile

Cost per mile equals kilowatt-hours per mile multiplied by the effective cost of a kilowatt-hour. The effective cost is not the number on the rate sheet. It is the energy rate plus your monthly demand charge spread across the kilowatt-hours you bought that month.Energy is straightforward: you consume it, you pay per unit. Demand is not. It is billed on the highest short interval of the month, usually fifteen minutes, in dollars per kilowatt. Nothing about it scales with how much you charge. Charge twice as much energy at the same peak and your demand bill does not move — which means the demand component per kilowatt-hour halves.That is the mechanism behind every strange result in fleet charging economics. A busy depot with a flat load has a small demand adder. A quiet depot that spikes hard for one hour has an enormous one. Two fleets with identical vehicles and identical routes can be a factor of three apart on cost per mile purely because of how their kilowatt-hours are spread across the month.

Here is the worked case, with every input stated as an assumption rather than a finding. Ten vans, ninety miles a day, twenty-two operating days a month, which is 19,800 fleet miles. Assume 0.55 kilowatt-hours per mile, so about 10,900 kilowatt-hours a month. Substitute your own telematics number; the point of the exercise is the structure, not these digits.Depot A sits on a rate with energy at eleven cents and demand at twelve dollars per kilowatt-month, and it runs managed charging that holds the site peak at 60 kW. Depot B sits on a rate with cheaper energy, nine cents, and demand at twenty-two dollars per kilowatt-month, and it charges every van at full port output the moment the shift ends, peaking at 190 kW.Depot B has the cheaper electricity and the more expensive charging. That is not a paradox and it is not unusual. It is what happens when a fleet negotiates the energy rate, which is visible, and ignores the demand rate, which is not.

Kilowatt-hours per mile is a measurement, not an estimate. Your telematics has it, and so do the session logs on networked chargers. If the vehicles are not on the road yet, manufacturer figures and the federal fuel economy database give you a starting point, but replace them with measured data in the first quarter. Cold weather, payload, terrain and idling accessory load all move this number, and they move it more than most fleets expect.The energy rate is on the bill, but read the rate schedule rather than the summary line. Time-of-use periods, seasonal rates and any dedicated EV rate change the answer, sometimes dramatically, and a depot that charges overnight is often eligible for a schedule that a general commercial account is not on by default.The demand rate is the input people skip, and it is the one that decides whether your cost per mile is good or embarrassing. Find the dollars per kilowatt on the invoice, then ask the utility two follow-ups: whether the tariff has a ratchet that carries a peak forward into later months, and whether there is a separate transmission or distribution demand component billed alongside the one you found.

Published averages tend to do two things wrong. They use residential or average commercial energy rates, which are not the tariff a depot sits on. And they leave demand charges out entirely, because demand is site-specific and awkward, which removes the single largest source of variation between fleets.The result is a tidy number that looks favourable and cannot be reproduced at any actual depot. A finance team that builds a case on it and then meets a real invoice loses confidence in the whole electrification project, which is a worse outcome than a conservative number would have produced.Build the number from your own tariff. It takes an hour, it survives contact with the first bill, and it tells you something the average never could: which lever to pull. If your demand adder dominates, the fix is scheduling, not a better energy contract. If your energy rate dominates, the fix is the rate schedule or the time you charge. You cannot tell which you are until you separate the two terms.

Managed charging first. Spreading the same kilowatt-hours across the dwell window lowers the billed peak without buying anything physical, and in the worked case above it removed more than half the cost per mile at Depot B.Rate schedule second. Ask the utility what schedules the account qualifies for, including any EV-specific or off-peak commercial rate. Moving schedules is paperwork rather than construction, and it occasionally beats every capital option available.Then the capital items: storage, if the peak that survives scheduling is short and the demand rate is high, and a service upgrade if you genuinely need more power rather than better timing. Both are slower and both should be argued against the cost per mile they actually remove, calculated the way this page calculates it.