How much electrical capacity do commercial chargers need?
More than the nameplate sum, unless you manage it. The NEC treats electric vehicle supply equipment as a continuous load, so conductors and overcurrent protection are sized at 125 percent of the load, and the feeder calculation uses the equipment nameplate or 7,200 volt-amperes per port, whichever is larger, with no diversity allowance for the fact that not everyone charges at once. Eight ports at 9.6 kW is not 77 kW of capacity; it is 96 kW. The exception is deliberate: where an energy management system limits the total, the calculation may use the managed maximum instead of the sum. That one provision is why one building needs a service upgrade and an identical building does not.
Updated 2026-08-20
The two numbers a proposal should put side by side
Almost every charging proposal shows one number, the nameplate sum, and then quietly sizes the service to something else. Ask for both, plus a third if load management is in scope.
The arithmetic, on one page
Here is the same handful of configurations counted three ways, so you can find yours and see the spread.
Per-port circuit sizing, because 208 volts is not 240
Commercial buildings are usually 208-volt three-phase, so the same charger delivers about 14 percent less power than the identical unit at a house. The circuit size does not change, because the circuit is sized on amps.
Why the code will not let you assume diversity
A residential range gets a demand factor because nobody runs every burner and the oven at once. EV supply equipment does not get one, because everybody plugs in when they arrive and the arrival times cluster.
What an energy management system has to do to count
An EMS earns its place in the load calculation by actually limiting the load, and the code has conditions.
How to tell whether your building already has room
You do not have to guess, and neither does your electrician. For an existing building, the code allows spare capacity to be established from measured demand rather than from a paper calculation of every load in the building.
When the capacity shortfall is real
Sometimes the building genuinely does not have it, and no amount of management invents power that is not there.
How much power does a commercial Level 2 charger use?
Between roughly 3 and 17 kW depending on the output setting and the building voltage. The common commercial configurations are 32, 40 and 48 amps, which at 208 volts deliver 6.7, 8.3 and 10.0 kW. The circuit has to be sized at 125 percent of that continuous draw, so a 48-amp port sits on a 60-amp circuit.
Do we need a new electrical service to add eight chargers?
Not necessarily, and the question is answered by measured demand rather than by the size printed on the switchgear. Establish the building's actual annual peak, compare it to the service rating, and see what headroom exists. Then decide between using that headroom at full output or using an energy management system to fit more ports into it. A service upgrade quoted before that exercise is an assumption.
Can we count on the fact that not every driver charges at once?
Not in the load calculation. The code gives EV supply equipment no diversity allowance, because charging demand is correlated: everyone plugs in on arrival and draws steadily for hours. The sanctioned way to get the same benefit is to control the total with an energy management system and calculate from the controlled maximum.
Does 208 volts versus 240 volts change how many ports we can install?
It changes the power each port delivers, not the circuit size, because circuits are sized on amperes. The practical effect is that a commercial 208-volt site delivers about 14 percent less energy per hour than the same hardware at 240 volts. On an overnight dwell that is usually invisible. On a four-hour dwell it is not.
How does DC fast charging change the capacity question?
Completely. A single DC fast port can draw more than the entire service of a small commercial building, and the equipment typically wants 480-volt three-phase supply. At that point the conversation moves from panel capacity to service capacity, transformers and the utility's interconnection queue, which is a different project with a different timeline.
Check the capacity line in your quote
If a proposal has a service upgrade on it, it is usually the largest single number on the page. Run your port count and site details through the estimate and you will have an independent range to hold that line item against.