Should You Turn Off Your Gas Furnace in the Summer?

When summertime comes, many people say goodbye to their gas furnaces and hello to their air conditioners.

But what about the proper shutdown process for your gas furnace? Is that even required?

It depends on what kind of furnace you have:

  • If you have an older gas furnace with a pilot light, then you should turn off the pilot light and the gas supply to the furnace. 
  • If you have a modern gas furnace with a hot surface ignitor, there is no shutdown process required. A hot surface ignitor uses electricity so it won’t run up your gas bill.

Why you should turn your furnace off if it has a pilot light

The pilot light is a tiny flame that stays on 24/7, regardless of whether your furnace is heating your home. The purpose of the pilot light is to provide an ignition source for your furnace’s burners when your furnace kicks on to heat your home.

When summer comes around, you won’t need to heat your home until the weather gets cold again. So there’s no point in leaving your furnace’s pilot light on.

Here are three reasons why you should turn off your furnace’s pilot light in the summer:

  1. Turning off your furnace’s pilot light ensures that your furnace doesn’t burn gas all summer long.
  2. The pilot light will generate small amounts of water vapor as a byproduct of combustion. The water vapor may condense inside your furnace and cause rusting (especially if you run your central air conditioner during the summer).
  3. The heat from the pilot light will heat up your home during the summer (it’s a tiny amount of heat, but still unwanted heat nonetheless).

How to turn off your furnace’s pilot light

First of all – if you’re going to turn off your gas furnace’s pilot light for the summer, make sure that there’s no cold weather coming. Some folks turn off their furnace too early in the year, only to turn it back on a couple of weeks later when the temperatures dip down again.

To turn off your furnace’s pilot light, open up your furnace and switch the pilot light knob on the gas valve to the off position. You should also turn off the furnace’s gas supply valve just to be sure that no gas leaks out of the pilot light.

Furnace gas valve in the open position
Turn your gas supply valve to the perpendicular position to close it.

How to turn your furnace off if it doesn’t have a pilot light

If your furnace doesn’t have a pilot light, then it probably has a modern electrical ignition system – such as a hot surface ignitor.

If your gas furnace has an electric ignition source, then you don’t need to worry about turning it off for the summer.

Your furnace won’t consume gas while it’s off if you have an electronic ignition source. You can turn off your furnace’s gas supply valve for the summer if you want to, but it’s not necessary.

Should you turn off your furnace’s power too?

If you want to save a little electricity, you can also turn off the power to your furnace. Your furnace’s control board draws a tiny bit of power while it sits there doing nothing. So if you are really strapped for cash, then turning off your furnace’s power during the summer will save you a few bucks.

However, if you have a central AC system in your home, then you should leave the power on to your furnace since a central AC uses the same air handler that your furnace does.

Hi, my name is Trey Lewis and I’m the founder and chief editor at HVAC Training Shop. My goal for this website is to help homeowners troubleshoot and maintain their home’s HVAC systems. Whether it’s changing an air filter, troubleshooting a blower motor, or just buying a new humidifier, I want to make sure that you’re covered.

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