Commercial energy / Buyer guidance
Natural gas demand and reservation charges: read the tariff determinant
Distinguish therm consumption from contract demand or reserved capacity and reconcile an original fixed-plus-variable gas example.
Do not import an electric kW formula into a gas invoice
An electric demand charge often uses a measured electrical demand determinant. A gas account may instead have charges connected with contracted quantities, transportation, reserved capacity or a utility-specific service design. The presence and calculation of any gas demand or reservation component must be verified from the actual tariff and agreement.
Start by naming the charge exactly as printed. Record its unit: therms, MMBtu per day, a contract quantity, a daily demand amount or another defined measure. Then identify the billing period and whether the amount depends on actual use or a reserved right. A fixed monthly cost can remain even when consumption falls.
Reconcile five pieces of the calculation
Obtain the applicable rate schedule and effective date, the agreement's contracted quantity, the unit price, the days or months billed and any minimum or adjustment provision. Keep transportation and commodity agreements together when they interact. A national gas price series cannot determine whether a utility applied a local reservation charge correctly.
Gas transportation service can have several options. Nicor rates and riders, for example, distinguishes services and storage arrangements. It is a concrete reference for why account-level documentation matters, not a universal tariff for this guide's readers.
Worked example: reducing usage does not necessarily reduce reservation cost
Hypothetical agreement: reserved capacity is 200 MMBtu/day, and an assumed reservation price is $0.10 per reserved MMBtu/day for each calendar day. For a 30-day billing month, the reservation amount is 200 × $0.10 × 30 = $600. Actual commodity use is 3,000 MMBtu at an illustrative $4/MMBtu, or $12,000. The two entered components total $12,600.
If consumption falls to 2,400 MMBtu and the capacity reservation is unchanged, commodity cost becomes $9,600 while reservation cost remains $600. Total becomes $10,200. The $2,400 modeled difference comes entirely from commodity consumption in this example. A different tariff may define the determinant or time unit differently; copying $600 into an actual invoice would be unjustified.
Questions before changing contracted capacity
- Is the reserved quantity sized for the coldest operating condition or only average use?
- Is a reduction allowed, and what notice or minimum commitment applies?
- Would it affect service firmness, restoration or curtailment exposure?
- Who has validated the operating load and safety requirements?
- Are there penalties, replacement purchases or other consequences for exceeding the contracted quantity?
Do not reduce a critical service reservation solely because annual use declined. Facilities, the utility and the authorized supplier must establish whether the operating requirement has changed. The gas peak-planning guide separates cold-day operating needs from annual commodity budgeting.
Sources and limits
Nicor's current rates and riders demonstrates service-specific schedules. FERC gas resources covers the interstate regulatory context. Every quantity, price and billing formula in the worked example is an explicit assumption rather than a quoted tariff.