Demand Charges on an Electric Bill: What Yours Actually Costs
Most of an electric bill charges you for energy: kilowatt-hours, added up over the month. A demand charge does something different. It bills the single highest rate of power your building drew during any one interval, usually fifteen or thirty minutes, and it charges that in kilowatts.
The practical consequence is that one interval out of roughly 1,400 in a month sets the entire charge. Everything else your building did is irrelevant to that line. A compressor and a chiller that happen to start within the same half hour can cost more than a week of steady running.
10 articlesUpdated AUG 10 2026
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01Is the Demand Charge on Your Ameren Illinois Business Bill Worth Attacking?Downstate Illinois businesses are served by Ameren Illinois, not ComEd, and the demand mechanics are not interchangeable. Here is what to read off your own bill before anyone sells you a way to reduce it.Read02Does Ameren Illinois Have Peak Hours, and Do They Cost Your Business Anything?Peak hours only cost you money if a charge on your bill is defined by them. Here is how to tell whether that is true of your Ameren Illinois business account before you reschedule anything.Read03Does ComEd Ratchet Your Demand Charge? What One Bad Month Actually CostsOn some utilities a single bad month sets your billed demand for a year. On ComEd's standard commercial delivery classes it does not. Which of those you are on decides whether preventing a one-off spike is worth paying for.Read04ComEd Demand Charges, Reconciled to the MeterSix real ComEd commercial demand charges, each reconciled against the site's own interval data. The measured on-peak demand equals the billed demand exactly, and the charge matches within ComEd's own rounding. Plus the one bill we refused to reconcile.Read05Can You Move Your Peak Outside ComEd's 9-to-6 Window, and What Would It Save?ComEd only bills demand on your highest half hour between 9 AM and 6 PM on weekdays. Power drawn outside that window sets nothing, which makes load shifting a real lever and caps what it can recover in a way most owners are never told.Read06Two Meters on One ComEd Site: Which Peak Actually Gets Billed?When a ComEd site has more than one meter, billed demand is the meters summed at the same half hour, not the sum of each meter's own maximum. That difference decides whether staggering equipment across meters saves you anything.Read07ComEd Demand Charge Calculator: Your Exact Distribution ChargeCalculate 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.Read08How Often the Demand Charge Misses a Business's Real Peak: Six ComEd Meters, Three YearsComEd bills the highest half hour between 9 and 6 on weekdays. Across six businesses and 214 billing months, the physical peak fell outside that window 69 times: a bowling alley 27 months out of 35, a weekend business 28 out of 41, a print shop never. Measured, by business type.Read09What is Peak Demand?What is peak demand? Peak demand is the highest electricity load recorded during a billing period. Learn how utilities calculate demand charges, see a worked example, and estimate load factor.Read10What Is a Demand Charge on an Electricity Bill?A demand charge bills your highest burst of power, not total usage. See how utilities measure peak demand, why one spike sets it, and where it appears.Read