What Interval Meter Data Analysis Shows
The analyzer at the top of this page reads your ComEd Green Button export and draws your load profile in seconds: the always-on floor that runs around the clock, whether your heating and cooling are electric, and the single interval that sets your peak demand. Analyzing interval meter data means reading that shape instead of a monthly total, so a decision about your electricity rests on what the meter actually recorded rather than an estimate. The sections below explain what the data is, how the meter records it, and what a load profile reveals.
Most people arriving here do not have the export yet, because it is not something ComEd puts in front of you. You have to ask for it and wait. If that is you, start with the document you already have: upload your bill to the free ComEd bill reader. It rebuilds every charge from the PDF, shows you what the bill can and cannot answer, and if you want the rest, it requests your interval data from ComEd for you. Come back here with the file when it arrives.
What Interval Meter Data Is
Interval meter data is a detailed record of electricity demand measured at fixed time intervals rather than summarized monthly. Utilities record the average power demand during each interval, typically every 15 or 30 minutes, and store those readings as part of the meter's historical usage data.
Instead of a single monthly total, interval data contains many measurements across the billing period. Each measurement represents the building's demand during one interval. The highest interval demand recorded during the billing cycle becomes the peak demand used to calculate demand charges on the electricity bill.
Utilities such as ComEd provide up to 24 months of this interval demand data for accounts with recording-type meters. When the data is analyzed or graphed, it reveals how a facility's electricity demand rises and falls throughout the day, allowing analysts to identify the specific events that create peak demand charges.
You can see this for your own home or business with the free analyzer at the top of this page. It reads your ComEd Green Button export and draws your load profile: the load that runs around the clock, whether your heating and cooling are electric, and when your day peaks.
How Electric Interval Meters Record Electricity Usage
Electric interval meters continuously measure the flow of electricity through a service connection. Instead of displaying only a cumulative total like older analog meters, interval meters record electricity usage over fixed measurement windows, typically 15 or 30 minutes.
During each interval the meter calculates the average power demand for that period and stores the value in its internal memory. Over the course of a billing cycle this creates a sequence of demand readings representing the building's electrical load throughout the day.
Utilities later retrieve these readings and use them to determine the highest demand recorded during the billing period. That value becomes the building's billing demand and is used to calculate demand charges on the electricity bill.
15 Minute vs 30 Minute Demand Intervals
Utilities record electricity demand in fixed measurement intervals, most commonly 15 or 30 minutes. Each interval represents the building's average demand during that window. Some utilities use 15-minute intervals, while others, including ComEd, record demand in 30-minute intervals. Regardless of the interval length, the highest recorded interval during the billing period becomes the building's peak demand used to calculate demand charges.
The most expensive electricity you use may last only thirty minutes.
What an Electric Load Profile Shows
An electric load profile is a visual representation of interval demand data. Instead of showing a single monthly total, the load profile reveals how a building's electricity demand rises and falls throughout the day.
Plotted across a billing period, most facilities hold a relatively low baseline demand for the majority of the month. A load profile makes the exceptions visible: a short interval where demand rises sharply above that baseline. Because utilities bill demand on the single highest interval, that one spike, often lasting only a single measurement window, becomes the peak demand for the entire period.
The same value then carries through to the electricity bill. The highest interval recorded by the meter becomes the billing demand, which is multiplied by the demand rate to produce the distribution demand charge.
The sequence is consistent across every commercial account:
- the electric meter records demand during each measurement interval
- the load profile reveals those measurements over time
- the highest interval becomes the billing demand on the electricity bill
A single short demand event can therefore determine the demand charge applied to the entire month.
How Interval Data Reveals Peak Demand Events
Peak demand events become visible only when electricity usage is measured at short time intervals. Monthly electricity bills report the highest demand recorded during the billing period, but they do not reveal when that peak occurred or what operational activity caused it.
Interval data exposes those events by showing how demand changes throughout the day. When the data is graphed as a load profile, short periods of unusually high demand appear as sharp spikes above the building's normal operating level.
These spikes often correspond to specific operational events inside the facility. Large motors starting, HVAC systems beginning their daily cycle, or multiple pieces of equipment starting simultaneously can briefly push demand far above the building's normal load. Because utilities determine billing demand using the highest recorded interval, even a short spike can determine the demand charge for the entire month.
By examining interval data, an analyst can identify the timing and magnitude of these events, and trace which loads overlapped to produce them. That is the information any decision about a peak would have to start from. Whether a given peak is worth acting on is a separate question, one the data informs rather than settles.
A Peak You Can Only Find by Summing the Meters
Interval data does something a monthly total cannot. It lets you line up separate readings by timestamp and add them. One reconciled ComEd site ran four meters, and each had its own thirty minute interval file. No single meter showed the site's real load. The billed demand, 242.57 kilowatts, was the highest combined draw across all four meters at the same instant, the site's true peak demand, at 2:00 PM, and it reconciled to the bill to the cent.
You cannot see that moment on any one meter, and you certainly cannot see it on the bill. It exists only when the four interval streams are aligned to the same thirty minute grid and summed. That is what interval data makes possible and a monthly summary makes impossible. Finding the one coincident interval, across every meter on the site, that the tariff actually billed.
How Do I Identify When My Facility Is Hitting Peak Demand Charges?
Take the highest interval in your own interval data, restricted to the hours your tariff actually bills, and then confirm that the interval you found reproduces the demand charge printed on the bill. Those two steps are the whole method. Everything below is the detail that makes them come out right.
Get the interval file for the billing period you are investigating. ComEd provides interval data in thirty minute readings for accounts with recording meters, going back up to 24 months. Requesting it is the slowest step and the only one that involves the utility.
Sum the meters before you go looking for a peak. If the site has more than one meter, no single file contains the site's load. Align the files on the same thirty minute grid and add them interval by interval, as in the four meter reconstruction above. Skipping this is how sites end up investigating an event that never set anything.
Restrict to the window the tariff bills. On ComEd's standard commercial delivery classes, billed demand is the highest thirty minute interval between nine in the morning and six in the evening on weekdays, holidays excluded. The largest reading in the raw file is frequently not the one that was billed. A spike at eight thirty in the morning, or at any hour on a Saturday, sets nothing. Sorting the export by kilowatts and reading the top row is the most common way to identify the wrong interval.
Take the maximum of what survives that filter and read its timestamp. That timestamp is the answer to the question. The intervals on either side of it show what was ramping into it, which is what turns a timestamp into an explanation.
Then prove it against the bill. Multiply the kilowatt figure by the demand rate for your delivery class and compare the result to the demand line on the bill for that period. ComEd's 2026 filed base Distribution Facilities Charge at Secondary voltage is $12.50 per kW for Small Load, $12.78 for Medium Load, $12.47 for Large Load, $11.49 for Very Large Load, and $11.63 for Extra Large Load. Your computed figure should land somewhat under the bill, by roughly three to fifteen percent in the accounts we have reconciled, because delivery service riders are added on top of the base rate. If it lands far off, the disagreement is information: usually the window is not what you assumed, a meter is missing from the sum, or the delivery class is not the one you thought. A reconstruction that cannot reproduce the bill has not identified your peak. It has produced a number.
The analyzer at the top of this page runs the middle steps on a single meter's Green Button export and returns the interval that sets the peak. The demand charge tool carries it through the last one, reconciling the recomputed charge against the bill.
Why Monthly Electricity Bills Hide These Patterns
A monthly electricity bill summarizes the outcome of the billing period, not the operational events that produced it. The bill typically reports two key numbers: the total energy consumed during the month and the single highest demand recorded during the billing cycle.
What the bill does not show is when that peak demand occurred or what activity inside the building caused it. A demand charge might be created by a single short event, such as equipment starting at the same time, but the bill only displays the final peak demand value used for billing.
Because the bill aggregates the entire month into a few summary numbers, the operational patterns that produced those charges are not visible. Two facilities could show the same peak demand on their bills while having completely different load behavior throughout the month.
Interval meter data preserves that missing context. By recording demand throughout the day, it reveals the timing and shape of demand events that determine the billing demand.
