Bills and Data Guides for Illinois Businesses

The bill is the best evidence a business has about its own energy account, and reading it deliberately prevents most costly errors. A commercial electric bill separates into groups — account and meter details, usage and demand, supply charges, and delivery and other charges — and keeping those groups straight is what lets a business tell a supply question from a delivery question, and a pricing problem from a billing error. A number quoted in isolation, without knowing which group it belongs to, is easy to misread.

Each group behaves differently. Supply responds to the market and to a supplier contract; delivery follows a regulated utility tariff and changes only when the utility’s rates change; demand responds to how and when the facility operates. Because they move for different reasons, a change to one does not move the others — which is why applying a supply-price difference to the whole bill overstates any effect, and why the first step in any review is simply to see how the total divides.

Usage data goes deeper than the monthly bill. For larger or load-shape-sensitive accounts, interval data reveals when energy is used across the day and year, which drives demand charges, capacity obligations, and whether time-of-use pricing could help. Interval data has to be reconciled to billed kWh before it can be trusted, and the raw export should be preserved with its timestamps and units documented so it can be relied on later.

A full twelve months of bills is far more useful than a single statement. A year captures seasonality — winter gas load, summer cooling demand — shows how billed demand moves across the year, and reveals whether any month looks anomalous. That history is also what a supplier needs to price an account accurately and what a demand review needs to find recurring peaks.

A worked way to read a commercial bill is to build a simple twelve-month table with a few columns: billing period, kWh, billed demand (kW), the supply subtotal, the delivery subtotal, and any taxes or riders. Filling it in from a year of statements does two things at once. It reveals the shape of the account — which months carry the demand peaks, how much of the total is delivery versus supply, whether any month is an outlier worth investigating — and it produces exactly the history a supplier needs to price the account and a reviewer needs to judge whether the current rate is exposed. The table is unglamorous, but it turns a stack of bills into a decision-ready picture.

Interval data is the next layer of resolution, and it answers a different question. The monthly bill says how much and what the single peak was; interval data says when, hour by hour. That "when" is where much of a commercial account’s cost is decided, because demand charges and capacity obligations depend on the timing of load, not just its total. Before interval data can be trusted, though, it has to reconcile: the sum of the intervals across a billing period should tie back to the billed kWh, within a small tolerance. If it does not, something is off — a units mismatch, a missing block, a timezone shift — and the analysis waits until it is resolved. Preserve the raw export, work on a copy, and document any correction.

Two cautions keep bill-and-data work honest. First, a pattern seen in the data is a hypothesis, not a proven cause — an overnight baseload or a mid-afternoon spike suggests something, but it should be confirmed with the people who run the facility before a conclusion or a savings estimate is attached to it. Second, usage data is customer-specific and confidential; it should be shared through a secure channel, with account identifiers stripped from any analytical sample, and a broker or supplier should be able to say who can see it and for how long.

One more habit separates businesses that control their energy cost from those that are surprised by it: reading the bill every month, not just at renewal. A quick monthly glance at usage, billed demand, the supply rate, and any new line item catches a rate-class drift, a misapplied charge, a supplier price that has quietly reset, or a demand spike worth investigating — while it is still small and easy to address. The bill is not only a record; it is an early-warning system, and using it as one is the cheapest energy-management tool a business has.

Reading the bill and the data well is not an end in itself; it is the input to everything else. Procurement, demand management, contract renewal, and error recovery all start from the same documents. These guides cover how to read a ComEd commercial electric bill field by field and how to request and use demand and interval data — turning the paper a business already receives into a usable, trustworthy basis for decisions, without inventing or estimating anything.