This is a great question which gets asked all the time regarding gas fireplaces and gas inserts. The short answer is that it really depends on individual and what they are trying accomplish by either leaving it on or turning it off. There are functional reasons for asking the question, such as “will it hurt my fireplace if I do or don’t turn it off”, and then there are monetary reasons. It depends on what you want to know.

Here is some basic information about leaving the pilot on or off…

Pilot OFF:

• No gas is being wasted so you are conserving energy and saving money!
• No heat is being generated by the pilot so the glass door on your fireplace will not be warm to the touch. Just one less thing to worry about when it is HOT out.
• With the pilot off, there are still trace amounts of gas molecules in the burner and pilot tubes of your fireplace. The gas companies add a chemical called Mercaptan to the gas which gives it that lovely odor we all know. Spiders are attracted to the smell of the Mercaptan and will sometimes build webs in the pilot and burner tubes when the flow of gas is off. So when you go to turn on your fireplace in the early fall or late summer, it will not work, and you will have to call you local installer to come service the unit. This will cost money.

Pilot ON:

• On a cool night you can flip the fireplace on to take the chill out without having to re-light the pilot.
• No chance for a spider to make a web in one of the tubes and clog the burner
• If the pilot is left on for long stretches of time, without actually turning on the main burner of the fireplace, a white film can develop on the inside of the glass. This is sulfur based film and if left uncleaned could possibly etch itself into the glass. The sulfur is a bi-product of the burning pilot and it can build up over time on the glass. If you see this develop, refer to your user manual (or look it up online) to find out how to clean the glass or risk having that white haze there forever.

The big questions that people are usually wondering about is how much gas does it use. Really, it is “how much to it cost per month for the pilot to run?”

You need to understand that most Gas Fireplaces have  pilot’s which use about 900-1100 BTU/hr. This is pretty powerful, and for good reason. The pilot must generate enough Millivolts of electricity to open and close the gas valve. This also means that it uses a fair amount of gas.

For a natural gas home, you pay for you gas by the Therm. A Therm = 100,000 BTU. So if you your pilot uses 1,000 BTU/hr and it is running for 24 hours a day, and 30 days a month, that comes out to be about 720,000 BTU. Divide that by 100,000 BTU to find the amount of Therms it uses (approximately 7.2). Then look at your gas bill and find out what you pay per Therm. Usually it is $1 and change. So you pilot can be costing you $7 to $10 per month.

Propane is a little bit different. Since propane is done by the gallon, the numbers are different. There are about 91,000 BTU in a gallon of propane. And the cost per gallon of propane is a lot higher than natural gas, floating somewhere around $3.05/gallon now. Doing the same math it would mean the pilot uses about 8 gallons of propane per month, which translates to about $24.00 in fuel cost.

Those are the facts to the best of my knowledge. For propane users, it seems to make sense to turn off the pilot light from a monetary point of view. Even if the pilot gets clogged while its off, it is a virtual wash in money having it serviced by a repair person. For natural gas customers it can really go either way.