The problem arrives at six in the evening
A delivery fleet leaves in the morning and returns at the end of the shift. On arrival, each driver plugs in their unit. With no management at all, every charger starts at full power in the same fifteen minutes.
Those fifteen minutes coincide, for much of the year and in many tariff regions, with peak hours or their start. It is the time when energy is most expensive and when the registered peak weighs most on your bill.
What makes the problem deceptive is that the energy involved is not much. It depends on the kilometers of each route and can be moderate. The capacity is not, because it is all drawn at once.
The same energy, two different bills
Do the math with round numbers. Twenty units that need 40 kWh each per night add up to 800 kWh. If they plug in together to 22 kW chargers, they draw 440 kW in the first interval (illustrative: 20 × 22). If those same 800 kWh are spread over eight hours of night, the average is 100 kW (800 ÷ 8).
Same kilowatt-hours, same vehicle ready at the same departure time. What changes is the peak the meter registers: in one case it adds to the afternoon load; in the other it falls in the hours when the plant is nearly empty.
What the tariff charges for each decision
Under the GDMTH tariff, energy is billed at three prices depending on the time of day —off-peak, mid-peak and peak— and capacity is billed on the maximum demand registered in fifteen-minute intervals. A single high interval sets the capacity and distribution charges for the period. We explain it in how to read the demand charge.
That is why unmanaged charging penalizes you twice: it buys energy at the most expensive time and it also raises the peak. Staggered charging does the opposite on both counts: it buys during off-peak hours, which in most regions means the early morning, and it does not touch the day's maximum demand.
This is the bill nobody models. Fleet proposals usually compare cost per kilometer against diesel using an average price per kWh. That average does not exist under GDMTH: there is a price per time period and a peak charge, and both depend on when the units plug in.
The charger as a controllable load
Charge management is not an accessory. The e-mobility provisions issued by the former CRE (Agreement A/108/2024) define a smart charger as one that communicates through protocols such as OCPP or OCPI. With that, you set a capacity ceiling for the whole yard and a priority by departure time: the unit that leaves at five charges first.
The Regulations of the Electricity Sector Law (Reglamento de la Ley del Sector Eléctrico), in article 197, allow e-mobility load centers to register as Controllable Demand, under the provisions issued by the CNE together with the Ministry. A yard that already operates with controlled charging is better prepared for that category than one that only switches on and off.
When the yard cannot charge everything overnight within the ceiling, the next piece is storage: it charges slowly during the day and delivers in the arrival window without raising the peak. It is sized on the measured profile, not on the vehicle spec sheet.
The data you need to gather
Per unit: kilometers per day, energy replenished each night, arrival time and departure time. For the site: twelve months of bills and one week of metering at the switchboard that would feed the yard, to see how much margin is left in the afternoon and early morning.
With that we build the curve for your case, not the one in this article, and decide the number of chargers, their power and the ceiling. It almost always comes out to fewer and lower-power chargers than the first quote includes. The engineering of that curve is the basis of our service for fleet charging.
Sources
Regulations of the Electricity Sector Law, DOF October 3, 2025, article 197.
Agreement A/108/2024, general administrative provisions on e-mobility, issued by the former CRE, DOF September 10, 2024, section 3.6. After the 2025 reform the regulator is the CNE: it is advisable to confirm the current procedure with it.
Structure of CFE's GDMTH tariff (energy by off-peak, mid-peak and peak periods; capacity and distribution charges). This article does not use rates.
If your fleet is a few units, they stay overnight at the plant and your facility's peak occurs during the day, scheduling charging after ten at night solves almost everything without software or a study. What is worth measuring first is your plant's peak at the time the units arrive: if it is already close to the contracted demand, any simultaneous connection will exceed it.
