Gas Fireplace Running Cost Calculator

A gas fireplace is one of the easier things in the house to price, because it burns about the same amount of gas every hour it's on high. What it costs comes down to how big the fireplace is, whether it runs on natural gas or propane, what you pay, and how long you run it.

This works it out. Pick your fireplace's size and fuel, enter your price and how many hours a night you usually run it. You get the cost per hour, a month of those evenings, and what the pilot light costs if you leave it lit.

Propane costs more to run than natural gas at typical prices, a bit over twice as much per hour for the same fireplace.

A fireplace burns its input rating every hour on high. The rating, in BTU per hour, is on a label behind the lower grille or in the manual. Most living-room fireplaces are around 30,000; inserts and bedroom units run smaller, around 18,000; wide linear and see-through models run to about 45,000.

Turn that into fuel. A therm of natural gas is 100,000 BTU, so a 30,000 BTU fireplace burns 0.3 therm an hour. A gallon of propane is 91,452 BTU, so the same fireplace burns about a third of a gallon an hour.

Multiply by your price. At $1.31 a therm, 0.3 therm is about 39 cents an hour. At $2.67 a gallon of propane, a third of a gallon is about 88 cents.

The pilot light. A standing pilot burns roughly 600 to 1,500 BTU an hour, around the clock, whether the fire is on or not. At 1,000 BTU that's 720,000 BTU a month, 7.2 therms of natural gas or about 7.9 gallons of propane.

Worked example. A typical 30,000 BTU fireplace on natural gas at $1.31 a therm, 4 hours a night: 39 cents an hour; 4 hours × 30 nights = 120 hours, about $47 a month. Leaving the pilot lit adds about $9 a month.

Cost per hour = rating ÷ 100,000 × price per therm (natural gas), or rating ÷ 91,452 × price per gallon (propane).

A month = cost per hour × hours a night × 30.

Pilot light a month = 1,000 × 24 × 30 = 720,000 BTU, converted and priced the same way.

Typical fireplace (30,000) on gas at $1.31: 39 cents an hour, $47 a month at 4 hours a night, pilot $9. On propane at $2.67: 88 cents an hour, $105 a month, pilot $21. Large (45,000) on propane, 8 hours a night: $1.31 an hour, $315 a month.

📎Sources:Natural Resources Canada — All About Gas Fireplaces (input ratings, pilot light gas use),Napoleon — Ascent direct-vent gas fireplaces (model input ratings),U.S. Energy Information Administration — Units and calculators (therm and propane heat content),U.S. Energy Information Administration — Heating Oil and Propane Update (residential propane prices)