Not all furnaces have pilot lights anymore
Modern furnaces fall into two categories: those with pilot lights and those with electronic ignition systems. If your furnace was installed before the mid-1990s, it almost certainly has a pilot light. If it was installed after 2000, it probably has electronic ignition instead. Furnaces built between those years could have either one.
The shift happened because electronic ignition is more efficient—it doesn't burn gas continuously to keep a flame alive. A pilot light wastes energy even when the furnace isn't heating. Electronic systems light the burner only when heat is needed, which lowers your gas bill and reduces wear on the equipment.
You can tell which type you have by looking at your furnace. If you see a small blue flame burning steadily inside the combustion chamber even when the heat isn't running, you have a pilot light. If you don't see any flame and the furnace only ignites when the thermostat calls for heat, you have electronic ignition.
Key Takeaways
- Furnaces built before the mid-1990s almost always have pilot lights; newer furnaces use electronic ignition instead.
- A pilot light burns continuously and wastes gas; electronic ignition lights only when heat is needed.
- You can identify which type you have by checking whether a small blue flame is always visible in the combustion chamber.
- Pilot light furnaces are cheaper to repair but cost more to operate; electronic ignition furnaces are the opposite.
- If your furnace won't start and has a pilot light, the flame may have blown out and needs to be relit by hand.
Why furnaces switched away from pilot lights
Pilot lights were the standard ignition method for decades because they were straightforward and reliable. A small gas valve stayed open, and a lit match or spark ignited the gas flowing past the pilot flame. The system worked, but it had a cost: the pilot burned gas 24 hours a day, even in summer when you weren't using heat.
Electronic ignition systems changed that equation. Instead of a constant flame, an electric spark or hot surface igniter lights the burner only when the thermostat detects that the house is cold. Once the burner ignites and the furnace warms up, the igniter shuts off. This cycle repeats as needed throughout the heating season.
The energy savings are real. A pilot light can account for 5 to 15 percent of your winter gas use, depending on how long your heating season is and how often the furnace cycles. Removing that waste was attractive to manufacturers and homeowners alike, especially after energy costs rose in the 1970s and 1980s.
Pilot light furnaces are still in use
Millions of homes still have furnaces with pilot lights. They're older equipment, but they work, and many homeowners keep them running rather than replacing a furnace that still heats the house. If you have one, you'll recognize the characteristic sound: a soft whoosh when the burner ignites, and the smell of natural gas (which is actually an odor added to the gas so you can detect leaks).
One advantage of pilot light furnaces is that they can operate without electricity. If the power goes out, the pilot light stays lit and the furnace can still heat your home, as long as you have gas. Electronic ignition furnaces need power to operate—no electricity means no heat, even if you have gas.
The downside is maintenance. Pilot lights can blow out from drafts, vibration, or a faulty gas valve. When that happens, the furnace won't start until you relight it. You can usually do this yourself by following the instructions on the furnace door, but it's one more thing that can go wrong.
Electronic ignition furnaces and their trade-offs
Electronic ignition systems are more efficient and require less hands-on maintenance than pilot lights. You don't have to worry about the flame blowing out, and you don't pay to heat gas that isn't being used. The igniter itself—either a spark electrode or a hot surface element—is a straightforward part that rarely fails.
The trade-off is that electronic ignition furnaces depend on electricity. If your power goes out, the furnace stops working, even if you have gas. This matters most in winter storms, when you might lose power and heat at the same time. Some homeowners in cold climates keep a backup heating source (a wood stove, space heater, or generator) for this reason.
Repairs can also be more expensive. If the igniter fails, you're paying for an electrician or technician to diagnose and replace it, rather than relighting a pilot yourself. The parts themselves are usually affordable, but labor costs add up.
How to tell what type your furnace has
The simplest way is to look inside the furnace. Open the access panel or look through the window (if your furnace has one) into the combustion chamber. If you see a small blue flame burning steadily, you have a pilot light. The flame should be about the size of your pinky finger and should be blue, not yellow or orange.
If you don't see any flame, or if the flame only appears when the furnace is actively heating, you have electronic ignition. You might see a spark electrode (a thin rod) or a hot surface igniter (a ceramic or metal element) instead of a flame.
Another clue is age. Check the nameplate on your furnace—it usually shows the year of manufacture. Furnaces from the 1980s and early 1990s almost always have pilot lights. Furnaces from 2000 onward almost always have electronic ignition. If you're not sure, a heating technician can tell you in seconds.
What to do if your pilot light furnace won't start
If your furnace has a pilot light and won't turn on, the first thing to check is whether the pilot is still lit. Look through the access panel or window. If the blue flame is gone, you'll need to relight it.
Most furnaces have instructions printed on the door or inside the access panel. The basic steps are: turn the gas valve to "Off," wait a few minutes for any gas to clear, then turn it to "Pilot." Hold a lit match or lighter near the pilot opening while turning the gas valve to "On." The pilot should ignite. Once it's lit, turn the valve to "On" to start the main burner.
If the pilot won't stay lit, or if it lights but the furnace still won't heat, the problem is likely a faulty thermocouple (a safety device that detects the pilot flame) or a gas valve issue. These are not do-it-yourself repairs—call a heating technician.
Upgrading from a pilot light furnace
If you have an older furnace with a pilot light, you don't have to replace it when ready. Pilot light furnaces are durable and can last 20 to 30 years with regular maintenance. But if your furnace is approaching the end of its life, or if you want to lower your heating costs, upgrading to a newer furnace with electronic ignition makes financial sense.
A new furnace with electronic ignition will be 10 to 15 percent more efficient than an older pilot light model. Over the life of the furnace, that efficiency gain can offset the cost of replacement. You'll also get better temperature control, quieter operation, and fewer maintenance headaches.
If you decide to upgrade, a heating contractor can help you choose the right size and efficiency level for your home. Installation typically takes a day, and you can usually keep using your old thermostat, though a programmable or smart thermostat will give you even more savings.
Frequently Asked Questions
Can I convert my pilot light furnace to electronic ignition?
Not easily. Electronic ignition requires different burner components, a new gas valve, and electrical wiring. The cost of retrofitting is usually close to the cost of replacing the furnace entirely, so most people choose replacement instead. A heating technician can give you a specific estimate for your model.
Is a pilot light furnace dangerous?
No, pilot light furnaces are safe when they're working correctly. The pilot flame is contained in a sealed combustion chamber, and the furnace has multiple safety devices to prevent gas leaks. If you smell gas, turn off the furnace and call your gas company or a technician when ready.
Why does my electronic ignition furnace need electricity if I have gas?
Electronic ignition systems use a spark or heating element to light the gas, and that requires electricity. The furnace also needs power to run the blower fan, control the thermostat, and operate safety sensors. Without electricity, none of these functions work, even if gas is available.
How often do I need to relight a pilot light?
A healthy pilot light should stay lit all season long. If you're relighting it more than once or twice a year, something is wrong—usually a faulty thermocouple, a drafty furnace location, or a gas valve issue. Have a technician check it.
Do new furnaces ever have pilot lights?
Rarely. Almost all furnaces manufactured in the last 20 years use electronic ignition. Some specialty furnaces designed for off-grid or backup heating might still use pilot lights, but they're the exception. If you're buying a new furnace, expect electronic ignition.