How much electrical capacity does a charging depot need?

Nameplate sum is a real number, and it is the number an unmanaged installation has to be designed against, because with no controller in the system there is nothing preventing that condition.It is not even the top of the range. EV supply equipment is a continuous load under NFPA 70 Article 625, so feeder and service sizing carries a 125 percent factor. Twenty ports at 9.6 kW is 192 kW of nameplate and 240 kW of service sizing.Managed peak does not depend on how many ports you install, because the ports are not the constraint — the energy and the clock are.

That is the provision the whole managed-depot approach rests on, and it is the reason a small controller can change the size of an electrical service.The language and the article reference depend on the edition your jurisdiction adopted. Older editions describe an automatic load management system within Article 625. The 2023 edition frames it as an energy management system under Article 750 and points 625.42 at it. Adoption is not uniform, not even within a state, so confirm which edition your authority having jurisdiction is enforcing before the design is drawn rather than at plan review.The practical requirement is the same across editions: the limit has to be enforced by the equipment, it has to be documented, and the setting has to appear on the drawings so an inspector can verify it. A promise from operations that they will stagger plug-ins is not a load management system and no inspector will accept it as one.Fix the setting in writing. If the controller caps the site at 120 kW, that number belongs on the one-line diagram, in the load letter to the utility, and in the commissioning record. It is the number the entire service size is justified by.

At 208 volts three-phase, capacity gets expensive quickly in conductor terms. At 480 volts the same kilowatts need under half the current, which means smaller conductors, smaller conduit, less trench cross-section and cheaper switchgear — at the cost of a step-down transformer for the 208 or 240 volt charging equipment.There is no universal answer, but the crossover arrives earlier than people expect. Once the service exceeds a few hundred amps, the conductor and conduit saving from 480 volts starts paying for the transformer, and the difference compounds with distance across the yard.

A depot with a maintenance shop, compressors and a wash bay has a daytime profile that overnight charging misses entirely — which is good news you can only claim if you have the data.Get the data rather than estimating it. Utilities hold interval metering data for commercial accounts, usually twelve months of it, and will generally provide it on request. That gives you the existing peak, the shape of the day, and how much of the existing service is genuinely spare.That request is also a good first contact with the account representative you will need later, and it costs nothing. Ask for interval data and the current rate schedule in the same email.Then add headroom deliberately rather than by rounding: headroom for the vehicles in the next order, headroom for the exception charger, and headroom for the fact that the fleet's energy will grow before the service does.

Oversize and you pay twice: once in capital for switchgear, conductors and possibly a transformer the operation will never use, and again in calendar, because a larger service is more likely to require utility infrastructure work and the transformer lead time that comes with it.Undersize and adding capacity means going back to the utility, back into the queue, and often back into the yard with a trench.The asymmetry is why the sensible design oversizes the passive infrastructure and sizes the active equipment tightly. Conduit, duct bank, pad space and spare breaker positions are cheap while the trench is open and expensive afterwards. Transformers and switchgear are expensive both times, so buy those to the number the arithmetic supports.Say both numbers out loud in the utility application: the connected load and the managed maximum. A utility that only sees the connected load will size its side for the connected load, and you will be quoted for infrastructure your controller guarantees you will never use.