Commercial energy / Buyer guidance
Natural gas volume tolerance: separate monthly bands from daily balancing
Test gas contract quantities, heating-value units and daily obligations with an explicitly hypothetical winter shortfall.
Identify which quantity is actually constrained
A gas volume review needs more than annual consumption. Ask whether the supplier has committed to a monthly quantity, a daily quantity, a percentage tolerance, or supply of actual requirements subject to defined exceptions. Read the commodity agreement alongside the utility transport service documents. A supply-volume provision and a delivery-balancing obligation answer different questions; passing one test does not establish compliance with the other.
The Nicor Gas transportation information identifies transportation as a distinct service context. It does not make every commercial gas account a transport account. Establish the actual tariff and account arrangement before applying transport terminology.
Keep the unit and the clock attached to every number
Write the unit next to each forecast: therm, dekatherm, MMBtu, Ccf or Mcf. Energy and volume units are not interchangeable without the applicable conversion. The EIA units reference distinguishes energy quantities from physical volumes. For account settlement, use the agreement's unit and the bill's actual conversion basis rather than assuming a universal heat content per cubic foot.
Also label the measurement period. A gas day, calendar day, billing month and delivery month may not share boundaries. Ask who forecasts usage, submits any nominations, monitors changes and responds to notices. If a supplier says balancing is included, identify exceptions, limits, notification obligations and any charges passed to the customer. Do not assume a monthly tolerance grants permission to ignore a daily instruction.
Worked example: a winter excess without an assumed penalty
Invented supply schedule: January reference quantity is 5,000 MMBtu; the stated monthly tolerance is plus or minus 10%. The upper boundary is 5,500 MMBtu. Actual January consumption is 5,900 MMBtu, so 400 MMBtu lies above that boundary.
Assume this fictional agreement prices only the 400 MMBtu excess at $8.00/MMBtu instead of $5.00/MMBtu. The incremental supply amount is 400 × ($8.00 − $5.00) = $1,200. If the agreement instead repriced the entire 900 MMBtu deviation from forecast, the same price difference would yield $2,700. That difference is why the exact settlement wording matters. Neither calculation predicts an actual invoice.
Now suppose one day's actual consumption is 280 MMBtu against 200 MMBtu scheduled. The 80 MMBtu daily difference is a separate record. Do not add an invented balancing penalty to the monthly example. Determine first whether the account has a daily balancing exposure, whose obligation it is, what the governing rule says and whether any already-billed amount would be duplicated.
Build a winter operating handoff
Before a production increase or boiler outage, prepare the dates, expected daily and monthly quantities, responsible contact and after-hours escalation route. Request written confirmation of the revised supply arrangement. Afterward, reconcile final meter data, supplier settlement and utility adjustments together. An estimated meter correction can change the quantity used in the test; retain the revised bill and the settlement recalculation rather than treating them as unrelated transactions.
Sources and limits
The linked utility and EIA references support the service and unit distinctions. The tolerance, prices and alternative settlement rules are teaching assumptions, not Nicor terms. The gas balancing guide addresses the separate balancing review. No general contractual immunity or achieved saving is asserted.