Demand Charges
Demand charges are a major component of many commercial electricity bills and are based on the highest level of power a building draws during a short interval, often fifteen or thirty minutes. Because utilities must maintain enough generation and grid capacity to supply electricity whenever it is needed, even a brief spike in demand can determine a large portion of a monthly bill. The articles in this section explain what demand charges actually measure, how utilities calculate peak demand, and why short intervals of high electricity use can dominate commercial electricity costs.
10 articlesUpdated MAR 12 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 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.Read03ComEd 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.Read04Can 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.Read05Two 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.Read06ComEd 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.Read07Will EV Chargers Wreck the Demand Charge on Your Illinois Business Bill?A commercial EV charger is a demand event, not an energy purchase. In ComEd territory the hours it runs decide whether it adds nothing to your bill or resets your peak by itself, and you can work out which from your bill and the charger's nameplate.Read08Is the Demand Charge on Your Ohio Commercial Bill Worth Attacking?An Ohio commercial demand charge is worth attacking only if it is a large share of your bill and your peaks are short. Both of those are answerable from the bill on your desk, before anyone sells you equipment.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