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What Is a Capacity Charge on a Commercial Energy Bill?

What a capacity charge actually pays for

Regional grid operators — PJM (mid-Atlantic), ISO New England, and NYISO among them — don't just balance supply and demand minute to minute; they also have to guarantee that enough power plants will physically exist a few years from now to cover the grid's worst-case peak, like the hottest afternoon of the summer when every air conditioner in the region is running at once. To fund that, these grid operators run forward capacity auctions, paying power plants (and sometimes demand-response resources) to commit to being available years in advance. The cost of those auctions then gets allocated back down to every business and household on the grid — that allocation is the capacity charge on your bill.

How your share gets calculated

Unlike a usage charge, your capacity charge isn't based on how much electricity you consume overall — it's based on how much you were drawing during the specific hours the grid operator uses to measure system-wide peak demand. In PJM, this is called your Peak Load Contribution (PLC), and it's set by your usage during the five highest coincident peak hours across the entire PJM system, typically summer afternoons between June and September. NYISO and ISO-NE use a similar approach, but base it on a single annual coincident peak hour rather than PJM's five. Because the measurement window is tied to when the whole grid peaks — not when your specific building peaks — a business can do everything right on its own schedule and still see a high capacity charge if its peak overlaps with the region's.

How it differs from a demand charge

Capacity and demand charges are easy to confuse because both are driven by a peak rather than total usage, but they measure different peaks for different reasons. A demand charge is set by your own single highest usage spike in a billing month, and it's billed by your local utility to cover the cost of the wires, transformers, and substations sized to handle that spike. A capacity charge is set by your usage during a handful of hours the regional grid operator designates as its system-wide peak, and it funds having enough power plants under contract for the whole region — not your local delivery infrastructure. A business can have a high demand charge and a modest capacity charge, or the reverse, depending on whether its own peak usage lines up with the region's.

Who typically sees this charge

Capacity charges show up almost exclusively in deregulated wholesale markets — PJM, ISO-NE, and NYISO territory are the main ones in the U.S. — and they're most visible to larger commercial and industrial accounts, since smaller businesses and residential customers are usually billed on an aggregated, averaged basis rather than seeing their own individual peak-hour usage translated directly into a line item. Whether you see it itemized at all also depends on how your energy is purchased: some fixed-rate supply contracts fold an estimated capacity cost into a single all-in $/kWh rate, while others pass the actual capacity obligation through separately, meaning it can shift from year to year as regional auction prices change.

Can you lower it?

Because your capacity obligation is set only by usage during the grid operator's specific peak-measurement hours, general conservation elsewhere in the year won't move it — the lever is reducing load specifically during the windows likely to be system peaks (hot summer weekday afternoons, in most territories), through demand response programs, on-site generation, or simply curtailing non-essential equipment on the highest-demand days.

Frequently asked questions