Two ComEd bills. One paid 19.31 cents a kilowatt hour all in. The other paid 18.52 cents. Nearly eight tenths of a cent apart, on the same utility, in the same territory, weeks apart.
The obvious conclusion is that somebody is on a worse deal. The obvious conclusion is wrong, and one line on the bill explains almost all of it.
The fixed floor
Two charges on a ComEd residential bill do not move with how much electricity you use.
| Line as printed |
Amount |
| Customer Charge |
$15.50 |
| Standard Metering Charge |
$3.87 |
| Total fixed |
$19.37 |
That $19.37 is charged whether you use 100 kilowatt hours or 3,000. It is the cost of being connected, metered and billed at all.
What happens when you divide it
A fixed charge does not have a rate per kilowatt hour. It acquires one, and the rate it acquires depends entirely on how much you used.
| Monthly usage |
What $19.37 works out to |
| 500 kWh |
3.87 cents per kWh |
| 953 kWh |
2.03 cents per kWh |
| 1,518 kWh |
1.28 cents per kWh |
| 3,000 kWh |
0.65 cents per kWh |
Same charge every month. Six times the apparent rate at the bottom of that table than at the top.
The two bills, taken apart
Now strip the fixed charges out of both bills and look at what is left.
|
Bill A |
Bill B |
| Usage |
953 kWh |
1,518 kWh |
| Total |
$184.03 |
$281.06 |
| All-in rate |
19.31 c/kWh |
18.52 c/kWh |
| Less fixed charges |
$19.37 |
$19.37 |
| Variable spend |
$164.66 |
$261.69 |
| Variable rate |
17.28 c/kWh |
17.24 c/kWh |
17.28 against 17.24. Four hundredths of a cent apart. For everything that actually scales with consumption, supply, transmission, delivery and every rider on the bill, these two accounts are paying the same price to within a rounding error.
The arithmetic closes cleanly:
- Gap in all-in rates: 0.7954 cents
- Explained by fixed charges spread over different usage: 0.7565 cents
- Everything else, combined: 0.0389 cents
Ninety-five percent of the difference between these two bills is one $19.37 charge divided by two different numbers.
What that means if you are trying to work out whether you are overpaying
Dividing your bill by your kilowatt hours gives you a real number. It is what you actually paid. But it is not a rate you can compare against anybody else unless they used the same amount of electricity you did.
A smaller user will always show a worse all-in rate than a larger user on identical terms. Not because they are on a worse deal. Because they are dividing the same fixed charge by a smaller number.
This has a consequence that surprises people: using less electricity makes your headline rate look worse. Cut your usage by a third and your total falls, which is what matters, but your cents-per-kilowatt-hour figure goes up. The bill rewards you and the ratio scolds you.
If you want to compare against another account, compare the variable rate: subtract the fixed charges first, then divide. That number is comparable. The all-in number is not.
Where the $15.50 comes from
The Customer Charge is not a number ComEd picks. It is a filed base multiplied by a stack of adjustment factors, and the filed sheet spells the formula out:
CC & ADJ = CC x (IDUF + DRAF + EDAF + TPAF + RBAFD)
For a Residential Single Family Without Electric Space Heat account in 2026, the filed bases are $13.26 for the Customer Charge and $3.52 for the Standard Metering Service Charge.
The five factors, each on its own informational sheet, for the June 2026 billing period:
| Factor |
What it is |
Value |
| IDUF |
Incremental distribution uncollectible cost |
1.0206 |
| DRAF |
Delivery reconciliation adjustment |
0.6785% |
| EDAF |
Excess deferred income tax adjustment |
0.0000 |
| TPAF |
Total plan adjustment |
6.551% |
| RBAFD |
Revenue balancing adjustment |
0.7668% |
They sum to 1.100563, which is the multiplier applied to the base.
Never quote the base as your rate. $13.26 is not what anyone pays. The filed base times the filed factors is, and on this bill that is a ten percent difference.
There is a second charge hidden inside the first
The Customer Charge line is not only the customer charge.
ComEd's informational sheet for the Energy Assistance Charge, which funds the Supplemental Low-Income Energy Assistance Fund under Rider RCA, carries this note:
The Energy Assistance Charge is included within the Customer Charge on retail customer bills.
For 2026 that is $0.80 a month for a residential customer. It was $0.64 in 2025, so it rose 25 percent in January. A nonresidential customer pays $8.00, and one whose demand reached 10 MW last year pays $300.00 a month.
None of that appears on the bill. It is inside the Customer Charge line, and the only way to know is to read the supplement.
What reconciles, and what does not
This is the part we will not smooth over.
Applying the multiplier above to the filed bases:
| Line |
Filed base |
Base x 1.100563 |
Printed |
Result |
| Standard Metering Charge |
$3.52 |
$3.8740 |
$3.87 |
reconciles exactly |
| IL Electricity Distribution Charge |
$0.00124 |
$0.0012751 |
$0.00128 |
reconciles exactly |
| Customer Charge |
$13.26 |
$14.5935 |
$15.50 |
does not close |
The Standard Metering Charge lands on the cent. The distribution tax charge, which uses a different and smaller factor combination, lands on the cent. Both confirm the multiplier is right.
The Customer Charge does not close. Base times factors gives $14.59. Add the filed $0.80 Energy Assistance Charge and it gives $15.39, against $15.50 printed. A residual of about eleven cents.
We are not going to tell you that is an error, because we cannot show that it is. The filed sheets we hold do not account for it, and something we do not hold may. What we will tell you is that two other lines on the same bill reconcile to the cent with the same factors, and this one does not, and that we are recording the gap rather than rounding it away.
Can it be avoided?
No, and this is the one line where that answer is structural rather than legal.
The Customer Charge and the Standard Metering Charge exist because connecting, metering and billing an account costs money whether or not the account draws power. Solar will not remove them. A battery will not remove them. Switching to a retail electric supplier will not remove them, because both are delivery charges.
The only thing that changes them is your delivery class, and that is set by your dwelling type and whether you have electric space heat, not by anything you decide month to month. For 2026 the filed Customer Charge base runs from $9.76 for a multi-family home without electric heat to $15.09 for a single family home with it. The filed bases for all four classes and all four delivery charges, 2024 through 2027, are recorded in the ComEd residential delivery service charges.
What this page was checked against
Both, and they disagree slightly, which is the finding.
The bases, the adjustment formula, the five factor values and the Energy Assistance Charge inclusion are quoted from ComEd's filed informational sheets, current through the August 2026 billing period. The printed amounts are from two real bills. Two of the three delivery lines reconcile between them to the cent. The Customer Charge is about eleven cents above what the filed sheets on hand explain, and that is stated rather than hidden.
The rest of the bill is covered in every line on a ComEd bill, explained. The largest line on a commercial bill works the opposite way, entirely variable and set by a single thirty minute interval.
