The natural gas cost calculator estimates your monthly and annual gas costs by appliance using BTU ratings and your local gas rate. Enter your appliance usage to see which appliances cost the most and your total monthly gas bill.
Gas Rate Settings
Check your gas bill for your rate. US avg: $1.20/therm.
Appliance Usage
Cost by Appliance
How to Calculate Natural Gas Costs
Natural gas appliances are rated in BTU (British Thermal Units) per hour. To find the cost, convert BTU to therms (100,000 BTU = 1 therm), multiply by hours of use, then by your gas rate per therm.
Finding your gas rate
Check your gas bill — look for "rate per therm" or "rate per CCF." If your bill shows CCF (hundred cubic feet), multiply by 1.02 to convert to therms. Your distribution company may charge separate delivery fees on top of the commodity rate.
Furnace dominates in cold climates
In northern states, the furnace typically accounts for 60-80% of annual gas use. A 100,000 BTU furnace running 8 hours/day uses about 8 therms/day or $9.60/day at $1.20/therm. Over a 4-month heating season, that's roughly $1,150. Upgrading to a high-efficiency furnace (95 AFUE vs 80 AFUE) can cut heating costs by 15-19%.
Water heater efficiency matters
A standard 40-gallon natural gas water heater uses about 400 therms per year at 60-64% efficiency. A heat pump water heater (electric) can provide the same hot water for half the cost in many states. Consider a tankless gas water heater (90%+ efficient) or heat pump if your water heater is over 10 years old.
FAQ
Is this natural gas calculator free?
Yes, completely free with no signup required.
What is a therm of natural gas?
A therm is a unit of energy equal to 100,000 BTU. Natural gas is sold by the therm or by CCF (hundred cubic feet). One CCF of natural gas typically equals about 1.02 therms. Your gas bill shows usage in therms or CCF — multiply CCF by 1.02 to get therms.
What is the average natural gas rate in the US?
The US residential natural gas rate averaged about $1.20 per therm in 2026, though prices vary significantly by state and season. Northeast states like Connecticut and Massachusetts often pay $1.50-$2.00/therm, while states like Idaho and Wyoming may pay under $0.80/therm.
How many therms does a furnace use per month?
A typical 80,000-100,000 BTU furnace running 8 hours per day uses about 6.5-8 therms per day, or 200-240 therms per month during heating season. Annual furnace usage varies dramatically by climate — a home in Minnesota may use 800+ therms/year for heating, while a home in Florida may use almost none.
Which gas appliance costs the most to run?
The furnace (for heating) is by far the most expensive gas appliance, typically accounting for 50-70% of annual gas usage in cold climates. Water heaters are second at 15-25%. Dryers, ranges, and other appliances together account for the remainder.