Does your depot need a service upgrade for EV charging?

Services get sized for the building that was planned, plus the growth nobody ended up needing, plus the designer's margin. Then the compressors got replaced with efficient ones, half the lighting went to LED, and a shift moved. Nobody re-measures. The result is a yard on an 800-amp service that has never been above a third of it.The electrical code recognises this. NEC 220.87 permits the existing load on a service to be established from the maximum demand actually recorded over the previous twelve months, rather than by recalculating every connected load from scratch. That is the section your engineer will use, and it is why the interval data is the first thing to go and get. Which edition of the code applies to you is a jurisdiction question, so confirm the adopted edition with the authority having jurisdiction before designing around a specific article.

EV supply equipment runs at close to unity power factor, so treating kVA as kW is a fair approximation for the charging load. It is not a fair approximation for motors elsewhere on the same service, which is one more reason to use measured demand for the existing side rather than adding up plates.

Twenty-five ports on a service somebody was about to spend six figures upgrading. That is the ordinary outcome of this exercise, and it is why the interval data request comes before the equipment conversation.One caution on the last row: twenty-five ports at full rate is the electrical answer, not the operational one. Whether twenty-five vans finish by dispatch depends on how much energy each needs and how long the window is, which is a separate calculation and usually the binding one.

NEC Article 750 covers energy management systems and Article 625 covers EV supply equipment; read together in the editions that contain them, they contemplate exactly this arrangement, where the maximum load a service sees is the maximum the management system permits rather than the total connected equipment. Adoption varies by jurisdiction and so does how readily an inspector accepts it, so raise it with the authority having jurisdiction early rather than presenting it as a finished design.The practical constraint on how low you can set the cap is not electrical, it is arithmetic. Total energy the vehicles need, divided by the hours in the charging window, is the minimum average power the site has to deliver. Set the cap below that floor and vans leave short.

Two yards with identical 800-amp services can get opposite answers, because one sits on a lightly loaded transformer and the other shares a heavily loaded one with the building next door. There is no way to work this out from your side of the meter.Put the question in the load letter along with the rest of it, and state your managed site cap rather than the connected total. The number you tell them is the number they will study.

The mechanism is a line-extension allowance in the utility's filed tariff: they estimate the construction cost, apply an allowance based on the revenue your new load is expected to produce, and bill you the difference. Sometimes the allowance covers all of it. Sometimes it covers none of it.Whatever the split, no federal money reduces it. The Section 30C credit terminated for property placed in service after June 30, 2026 and has no federal replacement, so any proposal that nets a federal credit against a 2026 or later project is wrong on its face. Utility make-ready programs, where a utility runs one, are the layer where money may still exist.