Therms measure energy
A therm equals 100,000 British thermal units. Gas meters often measure volume, while the utility applies a heat-content factor to bill energy in therms.
Separate variable and fixed charges
Commodity gas, delivery and riders may each vary with therms. The customer charge is usually fixed. Add the variable lines to find the effective marginal price per therm.
Weather drives comparisons
Heating-degree days and thermostat settings can dominate winter use. Compare similar weather periods or normalize by daily consumption before drawing conclusions.
Worked example: calculate the effective variable therm price
A bill with 60 therms, a $42 commodity charge and a $30 variable delivery charge has $72 in therm-dependent charges. The effective variable price is $72 ÷ 60 = $1.20 per therm before fixed fees, taxes or adjustments.
Do not convert CCF to therms with a universal one-to-one rule. The utility may apply a heat-content factor, and EIA distinguishes volume units such as Ccf from the energy unit therm.
Compare therms per day and weather context first; use the utility’s own conversion factor and tariff when volume units appear on the statement. Reproduce the bill line by line: therms × each variable rate, then add the customer charge, riders and taxes. If the recreated total differs, ask the utility which factor or adjustment is missing before assuming consumption caused the change.
Primary sources and scope
These links support the units or diagnostic method used above. They do not replace your provider’s current tariff, bill or safety instructions.
- EIA — Natural gas units ↗ — Defines Ccf, Mcf, Btu and a therm as 100,000 Btu.
- EIA — Degree days ↗ — Explains heating degree days as an indicator of heating demand.
This guide explains general billing math. Utility tariffs and local rules control your actual charges. Sources and update practices are documented in our methodology.
Read the methodology →