Estimate a monthly Illinois natural-gas bill from therms used and an approximate price.
Monthly gas bill = therms used × an approximate Illinois delivered price of $1.15/therm, plus any fixed charge. Delivered prices swing with wholesale markets and winter demand.
Bill
Bill = therms × price per therm + fixed charge
Approximate price only; check your utility's current tariff.
It is a state reference average. Your local utility sets delivery and commodity rates, which change monthly.
Rates are approximate state or national reference values. Local rates, exemptions and rules can differ, so treat the output as a planning figure only.