Businesses installing chargers reason about them as an energy purchase. How many kilowatt hours, at what price, how much does that add per month. That framing is fine for the energy line and it misses the charge that usually matters more.
A commercial charger is a demand event. It draws a large amount of power for a short time, and on a commercial account in ComEd territory the bill contains a line priced on exactly that: the highest half hour you drew, inside a specific window. A charger can add very little energy and still be the most expensive thing on your site, or it can add a great deal of energy and cost nothing extra on that line. Which one happens is decided by the clock.
The arithmetic that decides it, in two numbers you have
Your billed demand. It is on the delivery portion of your bill, in kilowatts. Call it your current ceiling.
The charger's rating. It is on the specification sheet, in kilowatts, and it is what the unit can pull at full output.
Now compare them. If the charger's rating is a large fraction of your current ceiling, then a single vehicle charging at full power during business hours will lift your site above its old peak, and the demand charge follows immediately. A 60 kW unit on a site whose billed demand is 80 kW is not a marginal addition. It is a potential 75 percent increase in the number your delivery charge is multiplied by.
If the rating is small relative to your ceiling, and especially if the site's own load has plenty of headroom under its peak, a charger may hide inside the existing shape and cost you nothing on that line.
That comparison is crude and it is enough to sort the easy cases before anyone quotes you anything.
Why the hours matter more than the kilowatt hours
Here is the part specific to ComEd territory, and it is worth more than any general advice about EV charging.
ComEd bills commercial demand on the highest half hour recorded between nine in the morning and six in the evening, Monday through Friday, holidays excluded. There is no off-peak demand component anywhere in the commercial delivery structure. Power drawn at eleven at night does not appear in the determinant at all.
The consequence is stark:
A depot fleet that charges overnight adds essentially nothing to the demand charge. The vehicles come back at six, they charge through the night, and every kilowatt of that draw lands outside the window that sets the bill. You pay for the energy. That is the whole cost.
A customer-facing or midday charger lands squarely inside the window, and one vehicle arriving at two in the afternoon can reset your billed demand for the month by itself. You do not control when it arrives, which means you do not control the charge.
Same hardware, same energy, entirely different bill. This is the single most useful thing to know before choosing where to put a charger and what to rate it at.
The four questions worth answering before you buy
Can the charging be scheduled? Fleet charging usually can. Public or customer charging usually cannot. That answer alone separates the low-risk case from the high-risk one, and you know it before you look at any data.
Is a smaller or power-limited unit acceptable? A charger that can be capped in software, or one rated lower to begin with, converts an uncontrolled demand risk into a known one. The vehicle charges more slowly. On an overnight duty cycle that costs nothing operationally.
Does the installation include any load management? Systems that cap total site draw, or that throttle charging when the building approaches a threshold, exist and are the standard answer to this problem. Whether they are worth their cost depends on the gap between your current peak and where the charger would take you.
What is your headroom actually worth? If your billed demand already sits well above your typical operating level, there may be room to absorb a charger for free. If your site runs close to its peak most of the working day, there is none.
How to turn that into a number
The version worth spending capital against reads the interval data behind your bill, adds the charger's expected draw at the hours it would actually run, and recomputes the billed demand under ComEd's own determinant. That produces the incremental demand charge for a site that already exists, month by month, rather than a vendor's estimate of it.
It also answers the question in the useful direction: not "what will the charger cost" but "what is the latest hour I can allow charging, and at what power, before it starts costing me." That is a specification you can hand to an installer, and it is the output of a demand reconstruction rather than of a brochure.
Do EV chargers increase commercial demand charges?
They can, substantially, because a charger draws a large amount of power in a short time and the demand charge is priced on your highest qualifying half hour. Whether it does depends on when the charging happens relative to the hours your utility uses to set billed demand.
Does overnight EV charging avoid demand charges in ComEd territory?
ComEd's commercial demand determinant looks only at weekday hours between nine in the morning and six in the evening, and there is no off-peak demand component. Charging entirely outside those hours does not set billed demand.
How big a charger can my building take without raising the demand charge?
Roughly, the gap between your current billed demand and your load level at the hours the charger would run. Establishing it precisely requires the interval data behind the bill, because the bill reports only the peak and never the headroom beneath it.
Is load management worth it for commercial EV charging?
It is worth exactly what it prevents, which is the increase in billed demand it holds off, month after month. That is calculable from your existing load and the charger's duty cycle before anything is purchased.
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