What to Do After a High PLC Year

Opening a bill and discovering that your capacity charges have jumped because of a high peak load contribution, or PLC, is a common and frustrating experience for Illinois businesses. The instinct is to fix it right away. The reality is that a capacity tag, once set, generally applies for the full delivery year and cannot be changed retroactively. This article lays out what you actually can do: understand why the tag is locked, learn when the next one is measured, plan reductions for that window, and verify that the figure you were assigned is correct.

First, Understand Why the Tag Is Locked

A capacity tag is measured from your facility's usage during the grid's peak hours in a defined period, and then it applies for a full delivery year. For ComEd customers, that measurement follows PJM's rules, since ComEd operates within the PJM Interconnection. Once PJM and your delivery utility have calculated the tag from those past peak hours, the number is fixed for its delivery year.

This is the single most important thing to accept after a high PLC year: the current tag reflects usage that already happened during peak hours that have already passed. No change to your operations now will lower this year's tag. If you would like a fuller explanation of how the measurement works, our guide on what a capacity tag is and how it is set covers it step by step.

Accepting that the current tag is locked is not defeatism. It redirects your energy toward the thing you can actually influence, which is the next tag.

Know When the Next Tag Is Measured

The next capacity tag will be measured during the upcoming set window, which for PJM historically falls during hot summer weekday afternoons when regional demand is highest. The exact peak hours are not known in advance and are confirmed only after the season ends.

Because of that uncertainty, the practical approach is to treat the whole likely peak window as the period that matters. Rather than waiting for a specific announced date, businesses that manage capacity costs prepare to reduce load across the afternoons most likely to become peaks. Coincident-peak alert services can help identify those days, a topic covered in our resource on capacity tag forecasting methods.

Marking the expected set window on your operational calendar, well before summer, is one of the most useful things you can do after a high PLC year. It turns a vague intention into a scheduled readiness effort.

Diagnose What Drove the High Tag

Before planning reductions, it helps to understand why the tag came in high. A few common causes:

• A process ran during a peak hour. A batch operation, a large motor, or simultaneous equipment startup that happened to coincide with a system peak can inflate the tag.
• No peak-hour awareness. If the facility was operating normally with no plan to reduce during likely peaks, the tag simply reflects business-as-usual load during the busiest grid hours.
• A one-time event. An unusual day, such as a temporary rental unit or a special production run, may have landed on a peak hour.
• Growth in load. If the business genuinely added equipment or shifts, higher peak-hour usage may be structural rather than accidental.

Diagnosing the cause matters because the response differs. A one-time event calls for making sure it does not recur during the next window. Structural growth calls for a longer-term look at whether any of that added load is flexible. Reviewing your interval data around the peak hours is the best way to see which category applies.

Plan Reductions for the Next Window

Once you know when the next window is and what drove the last tag, you can build a plan to reduce load during likely peak hours. The essentials:

1. Inventory controllable load. Identify equipment and processes that can be paused, slowed, or rescheduled for a few afternoon hours without harming safety, quality, or comfort.
2. Assign responsibility. Decide who watches for peak alerts and who executes the reduction when a likely peak is flagged.
3. Prepare a response. Document exactly what gets turned down or shifted, and confirm operations can tolerate it.
4. Consider technology. Where curtailing operations is not practical, some businesses use on-site energy storage to discharge during peaks so the meter reads lower while equipment keeps running. Our resource on how storage lowers capacity and transmission charges explains that option.

This is the same discipline described in our peak shaving material, applied specifically as a recovery plan after a high year. Remember that these reductions influence a future delivery year's tag, not the current locked one, so the benefit is forward-looking.

Verify the Tag Is Accurate

It is worth confirming that a high tag is actually correct rather than the product of a data or metering error. To do this:

• Request your interval usage data and your assigned capacity tag from your delivery utility.
• Compare the usage recorded during the peak hours against your own operational records for those days.
• Check that the figure is consistent with how your facility actually ran during the peak window.
• If something looks wrong, raise it with the utility, since it owns the meter and the calculation.

Verification is a low-effort step that can occasionally catch a genuine error. Even when the tag is correct, going through the exercise deepens your understanding of which hours mattered and how your facility performed during them.

Understand What Will and Will Not Fix It

A few clarifications help avoid wasted effort. Switching competitive suppliers will not change the tag itself, because a supplier affects only the supply portion of the bill, while the delivery utility and grid operator set the tag. Reducing usage on ordinary, non-peak days will not lower the tag either, since only peak-hour load counts. And no action taken now changes the current delivery year's tag.

What does help is consistent, well-timed load reduction during the next set window, verified data, and an understanding of how capacity fits into your overall costs. For the broader picture of how supply and delivery interact, see our overviews of commercial energy procurement and commercial demand charges.

Key Takeaways

• A high capacity tag is locked for its delivery year and cannot be changed retroactively.
• The next tag is measured during the upcoming summer peak window, with exact hours confirmed after the fact.
• Diagnose what drove the high tag, then plan load reductions for the next window.
• Verify the tag against your interval data, and remember that switching suppliers does not change the tag.

Sources

• PJM Interconnection
• ComEd
• Illinois Commerce Commission
• Plug In Illinois

This article is general educational information about managing capacity tags and does not promise any specific savings, rate, or outcome for your business.