Yes, a gas furnace uses electricity to ignite and power the blower fan and controls.
Most gas furnaces run on 120V circuits from your electrical panel, but they can be supplied power by a generator in a power outage. Most common generator sizes from 2,500 watts and larger can supply enough wattage to run a gas furnace.
How Much Electricity Does a Gas Furnace Use?
A gas furnace needs 75 and 800 watts to start and run. A dedicated 15 amp circuit is typically enough to cover minimum and maximum ampacity, though some need a 20 amp line. See full furnace electrical specs below.
Can You Run a Gas Furnace Without Electricity?
Yes, but only with a generator to supply electrical power. The furnace needs power to run its blower motor, control board, igniter, relays, sensors and other internal parts. It will not start without electricity.
What Happens to the Gas Furnace When Power Goes Out?
The furnace won’t work unless it can be powered by a generator.
Some homes have a generator wired directly to the electrical panel, and when in the event of a power outage, the system automatically, almost seamlessly, switches over to the generator.
Without a power source, the furnace won’t start because, to begin with, the thermostat won’t signal the furnace to fire up. They have electronic ignition and require electricity for all functions.
If you have a power outage in the middle of a heating cycle, the furnace will simply quit running. The fan will stop. The heat within it will slowly radiate out of it.
How Do You Heat Your House Without Power?
By powering the furnace or other heat sources such as a space heater with a generator. Or by using an alternate source for heat. A few are described below.
You can use a generator to run your furnace in a couple of ways.
First, the generator can be wired into your home’s electrical panel. In this setup, the furnace must have a transfer switch, which allows you to switch power input from the electrical panel to a generator.
Secondly, you can wire a plug onto your furnace power supply – the hot and the neutral wire. Then, the furnace can be plugged into the generator.
Alternate sources of heat in a power outage include:
Wood stoves and pellet stoves. If you live where outages are common in cold weather, consider having a wood or pellet stove installed.
Propane heaters. A simpler, less costly option is to buy a portable propane heater designed for indoor use. Small units can run off a 1lb propane bottle. Larger units, those that will run much longer, need a full-size 20lb or 30lb bottle.
Gas Furnace Electrical Specifications
Voltage: 120V circuit (110/115/120V)
Watts: 60 to 1,600 watts based on two factors. First, variable speed ECM motors use less energy than single stage PSC motors. Secondly, the larger the blower of any type, the more watts it draws.
Minimum circuit ampacity: 6 to 14 depending on furnace output
Minimum overload protection: 15 to 20 amps
Maximum overload protection: 20 to 30 amps based on model
Motor full load amps: 4.7 to 10 for starting and running
ECM motors: 60 to 600 watts, with most less than 450 watts. Minimum overload protection 15 amps
PSC motors: 425 to 1,600 watts, with most 500 to 900 watts. Minimum overload protection 15 or 20 amps
Does a gas furnace use a lot of electricity?
No. Average draw is between 400 and 800 watts, less than most space heaters. Most furnaces can be wired to 15 amp circuit and run on 6-14 amps.
How big of a generator do I need to run my furnace?
A minimum of 2,500 watts to run just the furnace. If you plan to power lights, an electric stove, water heater, other appliances and your devices, consider a larger generator of 3,500 to 5,000 watts or more.
Do I have to restart my furnace after a power outage?
No, probably not. The furnace is designed to automatically restart after a power outage. And most modern furnaces do not have a pilot light that has to be relit.
If your furnace doesn’t come back on when the power comes on, make sure the thermostat is calling for heat. If it is, and the furnace doesn’t start:
1). Check for a tripped breaker, and reset it if needed
2). Press the furnace’s reset button – usually a red button inside the cover of the furnace.
3). If those steps don’t bring the furnace back to life, you probably need an HVAC technician to solve the issue.
Are there heaters that don’t require electricity?
Yes. Portable propane heaters without fans radiate heat.
Some wood stoves and pellet stoves also radiate heat and do not require electricity to operate.