Will My Gas Furnace Work Without Electricity?

One summer the power went out in our family cottage and the gas stopped working. Up until that point, I figured we’d still be able to use the gas stove for cooking and take hot showers. I’m not an electrician — so, I did some research to find out if a gas furnace should work without electricity.

No, during a power outage it isn’t likely your gas furnace will work. Several parts of your heating system, though fueled by gas, use electricity. Blowers, relays, and circuit boards are examples of parts of your gas furnace that rely on electricity.

Come to find out, during a power outage, it is advised to turn off the electricity to your gas furnace. When the power is restored — consider the potential of a power surge or fluctuation in the grid that can damage electrical components on valuable appliances — including your furnace.

How Do I Tell If I Have a Gas?

There are two places to check for gas. The first is the water heater and the second is your furnace. Homes can have electric water heaters and gas furnaces so we’ll want to check both systems to be sure.

Water Heater

This is a good step to complete when the lights are on. Getting to know the systems in your home is a good idea. If you need help, call one of the local professionals and have them come over the walk you through your equipment.

If you want to have a go at it — press on!

Remove the small access panel from the front of the water tank. It’s located at the bottom of the tank and is usually held in place with one or two small screws. If you remove the panel and see a blue flame. That’s a pilot light, which means your water tank is fueled by gas. Also, without removing the panel you’d likely see a thick black pipe leading into the water heater. This is the gas supply line. In addition, gas water heaters have vents to remove the exhaust created from burning the gas. So, if a vent tube is coming out of the water heater that’s your third sign.

Electrical water heaters don’t have pilot lights, don’t have a gas supply line, nor do they have vents. They do have an electrical supply line going into the top of the tank. It’s likely a heavy gauge wire feeding into the top of the water heater.

Now, not to confuse things — if you see electricity coming into the top of the water tank and you see the gas supply line — it is possible you have an electric starter to ignite the burner versus a constant pilot light. Modern systems likely have this type of a setup as it is more efficient than wasting fuel on a pilot light. This would be a good point to reiterate that invitation to the local electrician and/or HVAC guy. Let them evaluate your system and tell you exactly what you have.

To that point — in my home, I don’t have a hot water heater because my boiler has a ‘tankless’ system — meaning it generates hot water on-demand. In that case, I’d need to look at my furnace for the presence of gas.


Similar to the water heater — you’re looking for a gas line that feeds your furnace with fuel. Alternatives could be the furnace is fueled by oil in which case you’d see a large 275-gallon oil tank in the basement near your furnace. Or, propane is an option, but those tanks can be buried and you’d have a smaller fuel line leading into the furnace.

If you’re not certain — call your local HVAC company to come out and take a look. I’ve never run into a technician who wasn’t willing to offer advice and/or give a tutorial. Ask questions, and have them show you a shutdown and restart of the system. The next time your power goes out you’ll be equipped with the know how to take action.

Will My Pilot Light Go out When I Lose Power?

Yes. Your water heater’s pilot light can go our when you lose power. A gas water heater has a safety device called a thermocouple (no need for a flux capacitor joke here). The termocouple’s job is to monitor for a pilot light, which then controls the flow of gas to keep the burner on. When the power goes out, the thermocouple loses power, the gas valve closes for safety, and poof — out goes the pilot light. 

Related Questions

How Do I Turn on My Pilot Light?

First, check for the presence of gas. If you smell gas, never attempt to light a pilot light. Leave the house, take everyone else out with you, and call the authorities. Don’t forget your pets!

If it appears safe, follow these steps to light your pilot light. Every furnace is different so the steps may vary. It’s best to locate a manual to know the exact steps for your system. Generally, these steps will be close:

  1. Turn control knob all the way ‘off’
  2. Allow any lingering gas to dissipate by waiting a few minutes
  3. Turn the control knob to the ‘pilot’ position. In this position, the knob can be depressed. Or, you might see a separate red ‘ignite’ button if you can’t depress the control knob
  4. Find the small gas line inside and the pilot is located at the end
  5. Use a long grill lighter while pushing in the control knob or depressing the red button
  6. Once lit, you can release the control knob or button and turn the control knob from ‘pilot’ to the ‘on’ position

Nice work! Your pilot light is back on. It is on, right?

How to I Keep My Gas Furnace Running During a Power Outage?

You’ll find a number of ‘hacks’ online for this, but I’m going to put my foot down. Many of those hacks aren’t safe and could kill a lineman working on repairing power lines. Those solutions feed electricity into a home, via a generator, without any safety mechanisms. In many cases, this is illegal and very dangerous.

A generator is a good solution; however, consult an electrician and install a generator transfer switch. So, when the power goes out, you cut-off the power to your main breaker and you feed into a smaller secondary breaker for emergency use.


The purpose of a transfer switch is to safely connect a generator to circuits in your home that are wired into the electrical panel. In the picture to the left, you have ten breakers to power items during a power outage. Work with an electrician to determine which breakers you can power with your generator. Ultimately, the transfer switch ensures you safely use generator power during a power outage without having to worry about back feeding the utility line.


When the power goes out, it’s necessary you know what systems you can and cannot rely on. When it comes to your gas furnace it’s equally as important to know how to get things started again when the power is restored.

If you can’t rely on your heating system, regardless of the fuel source, perhaps a portable generator is an option. At least you’ll be able to generate some heat and keep some other ‘mission critical’ items running.

For now, grab that manual and figure out that iron box downstairs. You’ll need the knowledge soon enough.

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