# How much per day does it cost to run pilot lights?

Every year at this time, and again in the fall, we have the question of when to turn off the pilot lights. And each year we try to guess what it costs us to run it on the days we don’t need it. Since the meter turns so slowly we can’t figure it. Also, the meter is in cubic feet and our bill is based on \$1.72 per therm, whatever that is.

Since it’s a guaranteed waste, I suppose we should just turn it off every morning and relight it every cool evening, but that’s overkill if it’s in the penny range.

Or, reversing the terms of the equation, if I wanted to save one dollar how many hours extra would I have to have the pilot off?

So much to say, so little organization skills.

First, it depends on the mechanism of your pilot light. (it sounds you’re talking about a gas furnace) Older systems had pilot gas taken after the furnace regulator. This gas “trickles” out of the tube and is burned off by the pilot light. If you have an older furnace, DO NOT EXTINGUISH THE PILOT LIGHT!! If you do, you will be allowing gas to “leak” withoug burning it off.

Newer furnaces (and furnaces serviced recently) have a shutoff valve. (added to older models during service) This valve is usually red. If you have this, it is safe to turn off the pilot light (don’t blow it out and leave the gas on).

Now as to the cost savings of this. I have no clue. Here’s what I do know. When I was a chemistry teacher, I had gas lines in the lab. These lines put out gas at 3 psi, which is not much pressure. (you could turn on the gas jet and completely block the flow of the gas by pressing your finger on the opening.) This also equates to a slow flow rate. However, if you lit the gas out of the end of the jet (without a lab burner attached) a cool flame about 2 feet long shot out.

Since the pilot light is MUCH smaller than a 2 foot flame (often smaller than a candle flame), it is safe to assume that the pressure (and thus flow rate) is quite small. What it is in cubic feet per minute (cfm), I don’t know.

I know I didn’t help you much, but maybe this will spur the next respondant.

Typical home natural gas appliances run at a gas pressure of about 4" water column. In other words, the gas is at sufficient pressure to push a column of water up a tube about 4 inches high. For reference, 1 psi is about 28 inches water column.

As I recall, a standard natural gas pilot has an orifice size of about .020 inches. Somewhere, I’ve still got my old piping manual that gives CFH for standard orifice sizes and pressures, but I can’t find it. It may be at my office. But I do know it’s not much.

If nobody else knows the answer (I’ll bet this is the kind of thing someone else around here besides me has worked with) I’ll try and find my book in the next few days and post it. Or your local gas company or the service company for your brand of furnace should be able to tell you.

Ugly

I wouldn’t worry about turning off your pilot lights, the savings won’t amount to a dollar a year. I can give you an example, we have a propane stove that is used once a year during canning season. The pilot stays on all year around and including canning season consumes less than five gallons of propane gas per year. Propane runs under much higher pressure than natural gas but the amount of gas used will be similar to natural gas.

Boiler or furnace?

Here’s a good link for all conversion problems.

http://www-sci.lib.uci.edu/HSG/RefCalculators.html
"Over 13,320 Calculators"

Which led to this

Energy Calculator, all appliances

Heating (Gas) Average Therms Per Hour x Hours Used Per Day x Days Used Per Month x Ave. Rate Per Therm + Ave monthly Pilot Light Cost = Your Ave. Cost Per Month

``````
th/hr hr/day days  \$/thm  pilot  cost/mo.
Wall Heater     0.21 x______x____x 1.72 + 5.43 = ____
Central Furnace 0.66 x______x____x 1.72 + 9.05 = ____

``````