Gas Bill Calculator Formula

Understand the math behind the gas bill calculator. Each variable explained with a worked example.

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Formulas Used

Usage Charge

usage_charge = therms_per_month * rate_per_therm

Total Monthly Bill

total_bill = base_fee + therms_per_month * rate_per_therm

Annual Estimate

annual_estimate = (base_fee + therms_per_month * rate_per_therm) * 12

Variables

VariableDescriptionDefault
therms_per_monthMonthly Therms Used(therms)50
rate_per_thermRate Per Therm(USD/therm)1.2
base_feeMonthly Base/Delivery Fee(USD)12

How It Works

How Natural Gas Bills Work

Gas bills typically include a fixed delivery fee plus a per-therm usage charge.

Formula

Monthly Bill = Base Fee + (Therms Used x Rate Per Therm)

One therm = 100,000 BTU of natural gas energy.

Worked Example

50 therms per month at $1.20/therm with $12 base fee.

therms_per_month = 50rate_per_therm = 1.2base_fee = 12
  1. 01Usage charge = 50 x $1.20 = $60.00
  2. 02Total bill = $12.00 + $60.00 = $72.00
  3. 03Annual estimate = $72.00 x 12 = $864.00

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