Bandwidth and Swing Clauses: The Usage Promise Hiding in Your Electricity Contract
A bandwidth clause, also called a swing clause, sets how far your actual monthly usage can move above or below the volume a supplier priced your contract on, commonly 10% to 25%, before you're billed a penalty rate on the difference. A 100% bandwidth means no penalty at any usage level. Size contracts to your lowest realistic month, not your average.
Say a Grand Prairie warehouse locks in a 24-month supply contract priced off 33,000 kWh a month. Example numbers to show the math, not a live quote. Buried in the contract is a 10% bandwidth: the supplier holds the quoted rate only as long as actual usage lands between 29,700 and 36,300 kWh a month. In month 14, the warehouse loses its anchor tenant and usage falls to 20,000 kWh, about 33% under the contracted floor of 29,700 kWh. That's a labeled example, not a live account, but the math is exactly how a bandwidth clause turns a locked-in rate into a four-figure penalty line on next month's invoice. We recommend treating the bandwidth clause as page one of any commercial quote, not fine print, because it's the term that decides whether a slow month costs you nothing or costs you real money.
What a Bandwidth Clause Actually Promises
Every fixed-rate commercial electricity contract in ERCOT is priced against an assumed volume: how many kilowatt-hours the supplier expects to sell you each month. The bandwidth clause, sometimes called a swing clause or a take-or-pay tolerance, sets how far your real usage can move away from that number before the pricing changes. Stay inside the band and you pay the contracted rate no matter what happens to your business. Step outside it, high or low, and the supplier is allowed to charge you differently for the volume that falls outside the tolerance. This is a normal, PUCT-permitted contract term used across Texas's competitive commercial market. The problem isn't that it exists. The problem is business owners sign the contract without ever asking what the actual number is.
100% Bandwidth vs a 10% or 25% Swing Clause
A 100% bandwidth means there's effectively no penalty zone: your usage can double, or drop close to zero, and you still pay the contracted rate on every kilowatt-hour you actually use. Suppliers offer that structure mostly to larger, well-established accounts with predictable load on interval data metering, and they price it a little higher per kWh to cover their own risk. Texas's commercial market keeps headline rates competitive, EIA puts the statewide commercial all-in average at 8.66¢/kWh versus the 14.19¢/kWh national average (EIA, 06/2026), and bandwidth is one of the main levers suppliers use to protect their margin at that price without raising the quoted rate itself. A 10% or 25% swing clause is far more common on small and mid-size commercial contracts, the kind a Waco restaurant or a Plano office suite signs. That tighter band gets the business a lower headline rate, but it means the supplier's rate commitment only holds within a fairly narrow window around the volume they quoted.
- A seasonal slowdown: a Fort Worth retail account that runs light in January and February after a strong holiday quarter.
- A closed or downsized location: a tenant vacates a suite in an Irving office building with its own ESI ID, and the remaining load doesn't fill the gap.
- An LED retrofit or new efficient HVAC system that cuts usage faster than the supplier's original model expected.
- A Midland or Odessa oilfield services yard that idles equipment during a slow quarter.
- An added shift or new tenant that pushes usage well above the contracted ceiling, tripping the band from the high side instead of the low side.
- A summer heat spike that pushes a Corpus Christi or McAllen account's cooling load past the upper band during peak months.
What Suppliers Charge When You Trip the Band
On the low side, most suppliers bill a shortfall charge, sometimes labeled an unbilled volume fee or a buy-through rate, on the difference between the volume you were contracted to use and what you actually used. On the high side, the extra kilowatt-hours usually get priced at the current market rate instead of your locked-in rate, which can hurt if you trip the band during an ERCOT summer peak. Consider a labeled example: a Waco restaurant contracted at 26,000 kWh a month with a 15% swing falls to 18,000 kWh in a slow January, about 31% under the contracted volume. If the shortfall fee runs even a cent and a half per kWh on the undelivered volume, that's roughly $120 in penalty charges on top of a bill that should have gone down, not up. As a further hypothetical, say a larger Midland account runs 55,000 kWh a month: the same percentage shortfall on a wider swing can turn into a four-figure line item, an illustration of scale, not a live account. None of this shows up as a clean, separate charge on page one of the invoice. It's usually buried in a line called something like 'contract true-up' or 'bandwidth adjustment.'
A '100% bandwidth' quote sounds like the safe choice, but read the fine print before you assume it protects you. Some suppliers cap that promise at a certain load factor, or only apply it to accounts on interval data metering, or exclude accounts that fall to zero usage. A business that signs believing it has unlimited flexibility, then finds out the protection only applies above a certain usage floor, ends up with the same shortfall bill as a standard swing-clause customer. Ask the supplier to show the exact contract language, not the sales sheet.
Size the contracted volume to your lowest realistic month, not your yearly average, and ask for the bandwidth to be measured on annual usage rather than a single month. A restaurant that runs 30,000 kWh in July and 18,000 kWh in January should never let a supplier build a contract around a 24,000 kWh average with a 10% band, because January will trip it every single year. Give your broker 12 months of actual usage history and let the contract get built around the real range, not the average.
- What is my exact bandwidth percentage, in writing, not just 'flexible usage'?
- Is the band measured monthly or averaged across the full contract term?
- What is the shortfall charge per kWh if I fall below the band?
- What is the overage charge if I go above the band, and is it tied to the ERCOT market price?
- Is there a carve-out if I close, sell, or downsize a location mid-contract?
A bandwidth clause you never read is the easiest way to lose the savings your fixed rate was supposed to lock in. Voltcheckr reviews the swing terms on every commercial quote we bring you, not just the headline rate.
Get My QuoteFrequently asked questions
A bandwidth clause, also called a swing clause, sets how far your actual monthly usage can move above or below the volume your supplier priced the contract on, commonly 10% to 25%, before the supplier bills you differently for the kilowatt-hours outside that range.
A 100% bandwidth means there's no penalty zone at all. You pay the contracted rate on every kilowatt-hour you use no matter how far your usage moves. Suppliers usually reserve this structure for larger accounts with steady load and price it slightly higher to cover the risk.
Closing or downsizing a location can drop usage far enough to trip the low side of a bandwidth clause, triggering a shortfall charge on the volume you didn't use. Ask for a location-closure carve-out before you sign, especially on multi-location or multi-ESI ID contracts.
Yes. Bandwidth is a negotiated contract term, not a fixed industry rule. A broker who brings 12 months of usage history to the supplier can usually get a wider band or get it measured on annual usage instead of a single month, which matters most for seasonal businesses.
Fixed-rate contracts almost always carry a bandwidth clause because the supplier is locking in a price against an assumed volume. Index contracts, where the rate floats with the ERCOT market, typically don't need one since you're billed at the market rate on actual usage either way.