ComEd Demand Charge Calculator: Your Exact Distribution Charge
Calculate your exact ComEd demand charge. Enter your peak demand in kW and your delivery class and get the Distribution Facilities charge straight from ComEd's tariff, the same ratebook we reconcile real bills to, to the cent. Not an average-rate estimate.
The calculator above gives you the exact ComEd Distribution Facilities demand charge for a given peak demand and delivery class. Enter your peak kW, pick your class, and you get the charge and the effective rate per kW, computed straight from ComEd's tariff. This is the same ratebook that reconciles real bills to the cent, not an average rate typed into a generic calculator. It shows you what ComEd charges; it does not sell anything.
How ComEd calculates a demand charge
Your ComEd demand charge is one line on the bill: the Distribution Facilities Charge. It is your billed demand in kilowatts multiplied by a rate per kilowatt set by your delivery class. Billed demand is the single highest interval of demand the meter recorded, and the rate is fixed by which class you fall in, which ComEd sets from your trailing twelve-month peak.
The rate is not a round number, and it is not a single published figure. ComEd starts from a base Distribution Facilities rate and then applies a set of adjustment riders, and starting with 2026 bills each rider is rounded to the cent on its own line before the lines are summed. That is why a generic calculator that multiplies your kW by an average rate lands a few cents to a few dollars off. This calculator reproduces the actual tariff, rounding and all, so the number matches the bill.
How to calculate your peak demand charge
You need two things: your peak demand in kilowatts and your delivery class.
Your peak demand is the highest interval on the bill's demand line, or the single highest thirty-minute interval in your meter data. Your delivery class is set by the kW band your trailing twelve-month peak falls in: Small Load up to 100 kW, Medium Load 100 to 400 kW, Large Load 400 to 1,000 kW, and larger classes above that. Find the Retail Delivery Service line on your bill and the band next to it is your class. Enter both above and the calculator returns the exact charge and the effective rate per kW behind it.
To see how that peak compares to how you run the rest of the month, the same two bill numbers feed our load factor calculator, which turns them into the shape of your usage.
Why this is exact and generic calculators are not
Most demand-charge calculators multiply your kW by a single rate someone typed in once. That rate goes stale the moment ComEd files a new one, and it never captures the rider rounding. The rate this one uses is the rate ComEd actually billed: a committed ratebook, reconciled against real bills to the cent. Where a class or year is not loaded and proven that way, the calculator says so rather than guess. A number that matches the bill is worth more than a number that is merely close.
How is a ComEd demand charge calculated?
It is your billed demand in kilowatts times the Distribution Facilities rate for your delivery class. Billed demand is the highest interval the meter recorded in the period. The rate is a base rate adjusted by ComEd's riders; on 2026 bills each rider is rounded to the cent on its own line, then summed. The calculator above applies the exact tariff and rounding for the class and year you pick.
What is my delivery class?
ComEd assigns it from your trailing twelve-month peak demand: Small Load up to 100 kW, Medium Load 100 to 400 kW, Large Load 400 to 1,000 kW, Very Large Load 1,000 to 10,000 kW, and Extra Large Load above that. The Retail Delivery Service line on your bill shows the band.
Why does your number match my bill when other calculators do not?
Because your number comes from ComEd's actual ratebook and rounding, not an average rate. Generic calculators multiply by one stale figure and skip the per-rider rounding, which puts them off by a few cents to a few dollars. That same ratebook is reconciled against real bills to the cent.
What if my class or year is not covered?
The calculator tells you honestly rather than estimate. Only rates that stand up against a real bill are shown, so a class or year that is not loaded yet says exactly that. If you hit one, the gap is named on the spot and loading that class moves to the front of the line.