A demand charge is what a utility bills you for the highest rate at which you drew power during the billing period — measured in kilowatts (kW), separate from the energy you consumed (kWh). On a commercial and industrial (C&I) account it's frequently the single largest line on the bill, sometimes 30–70% of the total. It exists because the utility has to build and maintain enough capacity to meet your peak demand even if you only hit that peak for fifteen minutes a month — and the demand charge is how it recovers the cost of that standby capacity.

This guide explains what a demand charge is, why it's often bigger than your energy charge, the types you'll encounter, and the levers that actually reduce it.

#Demand vs. energy: the core distinction

The difference between demand and energy is the difference between rate and volume.

  • Energy (kWh) is how much electricity you used over the month — volume. Billed in $/kWh.
  • Demand (kW) is the fastest you used it — the highest power draw, usually averaged over a 15-minute interval, at any point in the period. Billed in $/kW.

An analogy: energy is the total water that came out of the tap over a month; demand is the widest you ever opened the faucet. The utility has to size the pipe for the widest moment, regardless of total volume — so it charges for both.

This is why two businesses with identical monthly kWh can have very different bills. A business that draws power steadily has a low peak. A business that spikes — a machine shop firing up heavy equipment at 8am, a cold-storage facility cycling compressors — hits a high peak for a short window and pays for it all month.

#Why the demand charge is often the biggest line

Three reasons demand can dominate a C&I bill:

  • Capacity is expensive. The utility's cost is driven by peak load, not average load, so the demand rate ($/kW) is set high to recover infrastructure cost.
  • One spike sets the whole charge. Demand is billed on the maximum interval, so a single fifteen-minute peak determines the charge for the entire month. There's no averaging-out.
  • Ratchets extend the damage. Many tariffs bill demand as a percentage of your highest peak over the trailing 11–12 months — so one bad month follows you for a year (see below).

For a facility with spiky load, the demand charge can exceed the energy charge outright. That's the case where reducing demand matters more than reducing consumption.

#Types of demand charges

Not all demand charges are computed the same way. The main variants:

#Non-coincident demand

Your own highest peak during the billing period, whenever it occurred. The most common form — the utility simply bills the single highest interval you hit.

#Coincident demand

Your peak measured only during the utility's system-peak window (e.g. summer weekday afternoons). The utility cares most about your draw when the whole grid is strained, so it bills your demand during those specific hours — which means a peak at 2am might not count, but a peak at 4pm in August does.

#Demand ratchet

A floor, not a separate charge. A ratchet bills your demand as a percentage — often 80–100% — of your highest peak over the trailing year, not just the current month. One high-demand month sets an elevated floor you keep paying against for up to twelve months, even in months your actual peak was far lower. If a demand charge looks too high for the month's usage, an earlier month's ratchet is the usual cause.

#Power-factor adjustment

A surcharge (or credit) tied to how efficiently your load uses power. Loads with poor power factor — lots of motors and inductive equipment — draw more current than their real power use implies, and the utility bills for the inefficiency.

For how these print and where to find them on an actual bill, see how to read a commercial utility bill.

#How to reduce a demand charge

Because the charge is set by your peak, reducing demand is about flattening or shifting that peak — not using less total energy. The levers, roughly in order of how commonly they're used:

  1. Peak shaving with storage. A battery discharges during your peak interval to cap how much power you pull from the grid, lowering the billed demand. This is the dominant lever for C&I storage economics, and it's why demand charges drive much of the behind-the-meter battery market.
  2. Load shifting. Move flexible, high-draw operations off your peak window — run them at night or stagger equipment startups so they don't coincide. Shifts the peak rather than capping it.
  3. Peak staggering / sequencing. Avoid starting multiple large loads simultaneously. Sequencing equipment startups keeps several smaller peaks from stacking into one large one.
  4. Power-factor correction. Install capacitors or correction equipment to improve power factor and remove the associated surcharge — relevant for motor-heavy facilities.
  5. Solar (partial). On-site solar reduces demand only to the extent your peak coincides with sunshine. For a facility that peaks at 4pm in summer, solar helps; for one that peaks at 7am or after dark, it does little for demand — which is why solar-plus-storage, not solar alone, is the usual demand-reduction case.

The common thread: every lever targets the peak, because the peak is the charge. Reducing total consumption barely moves a demand charge if the peak stays the same.

#Why demand charges matter for solar and storage economics

For anyone evaluating a C&I solar or storage project, the demand charge is often where the savings case lives — or fails to. A proposal that models savings against a blended energy rate and ignores the demand component will misstate the value of storage, because storage's biggest contribution is usually peak shaving, not energy offset.

This is also why measuring the savings is harder than it looks: the demand reduction depends on whether the battery actually discharged into the right interval, on the specific tariff's demand structure, and on whether a ratchet is in play. Getting it right means reading the demand component off the actual bill — line by line, against the actual tariff — not estimating it from a rate, which is exactly what bill-level savings verification does.

#What Tariform does

Tariform is a utility-bill intelligence platform. Demand charges sit at the center of both products on it.

Extract turns utility-bill PDFs into line-itemized, tariff-aware data — including the demand component broken out by type, mapped to its tariff role, and reconciled against the bill total. It's built for project finance analysts, consultants, and solar sales engineers who need defensible demand figures for pro-formas, deliverables, and proposals.

Verify is for C&I solar-and-storage portfolio operators who need to prove how much each system actually saved — including how much the battery's peak shaving reduced the demand charge — measured against the actual bill, every site, every month.

If you're sizing or selling a storage project and need the demand numbers to be defensible, book a demo — twenty minutes, a real bill, you see the output.

#FAQ

Do I still pay a demand charge in a month my facility was mostly closed?
Often yes. A demand ratchet bills against your highest peak over the trailing year regardless of the current month, and many tariffs carry a minimum or contract-demand floor. Without a ratchet or minimum, the charge tracks whatever your highest interval was — which can be low, but is rarely zero if any equipment ran at all.
Is demand really measured over just 15 minutes?
On most US tariffs, yes — the meter records your average draw in 15-minute blocks and bills the highest one. Some utilities use a 30- or 60-minute interval, and a few measure instantaneous peak. The interval length matters: a brief surge that wouldn't move a 60-minute average can set a 15-minute peak, so it's worth checking which your tariff uses.
Can a one-time event set my peak for the whole month?
Yes. A monthly generator test, commissioning a new chiller, or a single hot afternoon when everything ran at once can establish a peak you pay against for the entire billing period — and, under a ratchet, for up to a year. There's no averaging-out; the single maximum interval is the charge.
Does every commercial account have a demand charge?
No. Demand charges usually apply above a size threshold — many utilities move an account onto a demand rate once peak load crosses something like 20–50 kW, while smaller accounts stay on energy-only rates. If your load is growing, crossing that threshold can introduce a demand charge you didn't have before, which is worth anticipating rather than discovering on a bill.
Will adding solar without storage lower my demand charge?
Often less than expected. Solar only reduces the billed peak if your peak interval lands in strong sunlight, and you can't count on it being there at that moment — a passing cloud during your peak leaves the demand charge intact. Many C&I sites also peak in the early evening as solar fades. Solar rarely raises demand, but reducing it dependably is a storage job.
How do I find out how much of my bill is demand — and how much a battery could save?
Read it off the bill, not a blended rate: pull the demand line items by type, check for a ratchet or a coincident-peak window, and compare against your interval peaks. That line-by-line calculation against the actual tariff is what Extract and bill-level savings verification do.