Level 2 or DC fast charging for a fleet depot?

Delivered power is not the breaker size. NFPA 70 Article 625 treats EV supply equipment as a continuous load, so a 40-amp charger sits on a 50-amp circuit and delivers 9.6 kW at 240 volts. Use the delivered figure in the division.DC times in the table below are nameplate arithmetic, and real sessions do not hold that rate the whole way. Charging tapers as the pack fills, generally hard above roughly eighty percent state of charge, and the vehicle's own acceptance rate — not the charger's rating — sets the ceiling. A 150 kW port serving a vehicle that accepts 80 kW is an 80 kW port that cost like a 150 kW one.

Electrical infrastructure is reported at 40 to 60 percent of a DC fast project's total cost. That gap is the whole argument: at the midpoints, one DC port buys roughly a dozen Level 2 ports. If your vehicles sit for ten hours, that trade is not close.The cost driver differs as well as the amount. On Level 2 the spread inside the band is trench length and conduit run — a civil number that a good yard layout controls. On DC fast the spread is service capacity, and service capacity is a utility decision on a utility calendar.

The exceptions are real and they are not rare. A van comes back at ten percent because the route was changed. A unit gets reassigned to a second shift and has ninety minutes on the yard. A vehicle goes out on a Sunday nobody planned for. Level 2 cannot recover any of those inside the window, and the alternative to a DC port is a vehicle that does not go out.Sizing the exception bank is a frequency question. Count how often, across a month of dispatch records, a vehicle would have needed more energy than its window could deliver. Two DC ports covering a forty-vehicle yard is a common shape, but the count comes from your exception rate rather than from a ratio.There is a second reason to put at least one DC port on a depot: it de-risks the rest of the design. If an exception path exists, you can size the Level 2 bank against the ordinary night rather than the worst night, and the ordinary night is a much cheaper building.

A single 150 kW port is roughly the connected load of a small commercial building on its own. That usually means new switchgear, frequently a new or upsized transformer, and a utility interconnection process rather than a permit and an inspection.The transformer is the item that sets the schedule, and it is worth getting a dated lead time in writing before design freeze rather than after.It also changes the electrical room, the pad, the clearances and the heat rejection. DC equipment has larger footprints and working-clearance requirements, and the cabinet is not always adjacent to the dispenser.None of that appears on a hardware quote. It appears on the make-ready line, which is the part of a commercial charging project that routinely exceeds the chargers themselves.

Fit 19.2 kW ports to a fleet whose onboard chargers accept 11 kW and you bought conductors, not charging. Check the onboard AC acceptance rate on every vehicle in the order before specifying port amperage. It is a datasheet line and it is the most common reason a depot underperforms its design.DC bypasses the onboard charger entirely and feeds the pack directly, which is why it can go so much faster and why it costs what it costs. It also puts the conversion equipment, the cooling and the maintenance burden on your side of the connector rather than the vehicle's.Connector standard matters less than people expect and should not drive the decision. Adapters and dual-standard dispensers exist, and mixed-standard fleets are normal. Specify the standard your vehicles use, keep the option to change dispensers later, and do not let a connector debate delay a utility application.

The two decisions interact. A DC port used at midday sits inside most utilities' peak demand window and can set a monthly billing peak large enough to change the operating economics of the whole yard.Which is an argument for treating the exception bank as an exception bank rather than as a convenience, and for putting a hard site power cap in place before anything is energised.