Most modern gas furnaces don't have pilot lights anymore
If your furnace was installed in the last 15 to 20 years, it almost certainly does not have a pilot light. Newer furnaces use electronic ignition instead — a spark or hot surface that lights the burner only when the thermostat calls for heat. The pilot light was the older method: a small flame that burned continuously, waiting to ignite the main burner when needed.
Furnaces made before the mid-2000s often still have pilot lights, and some older models still in use today rely on them. If you have an older furnace or are not sure what you have, you can look inside the combustion chamber (the area where fuel burns). A pilot light looks like a small, steady blue flame about the size of a match flame. If you see that, you have a pilot light furnace. If you see no flame and the burner only ignites when heat is called for, you have electronic ignition.
The shift away from pilot lights happened because electronic ignition is more efficient — it does not waste gas keeping a flame alive 24/7 — and more reliable. Pilot lights can blow out from drafts, vibration, or wear, leaving you without heat. Electronic systems rarely fail in the same way.
Key Takeaways
- Furnaces built after roughly 2005 use electronic ignition and have no pilot light at all.
- Older furnaces with pilot lights have a small blue flame that burns continuously in the combustion chamber.
- A blown-out pilot light stops heat production entirely, but electronic ignition systems do not have this failure mode.
- If your furnace has a pilot light and it goes out, you can often relight it yourself by following the instructions on the furnace door.
How to tell if your furnace has a pilot light
The easiest way is to look at your furnace manual or the label on the furnace itself. The label usually lists the ignition type. If you do not have the manual, you can look inside the furnace access panel (usually a removable cover on the front or side). Turn off the furnace first, wait a few minutes for any residual heat to dissipate, then carefully open the panel and look into the combustion chamber — the enclosed space where the burner sits.
In a pilot light furnace, you will see a small blue flame burning steadily even when the furnace is off. In an electronic ignition furnace, you will see no flame at all when the system is idle. When the thermostat calls for heat, you may hear a clicking sound (the spark ignitor) or see a brief glow, but there is no continuous flame.
If you are uncomfortable opening the furnace or cannot locate the combustion chamber safely, call a heating technician. They can tell you in seconds and can also check whether your ignition system is working properly.
What happens when a pilot light goes out
A pilot light furnace will not produce heat if the pilot light is out. The main burner cannot ignite without that small flame to light it. You will notice the furnace running (the blower may turn on) but no heat coming from the vents, or the furnace cycling on and off without warming the house.
Common reasons a pilot light goes out include a draft from an open door or window, a clogged pilot opening (usually from dust or debris), a failing thermocouple (the safety device that detects the pilot flame), or a problem with the gas supply. Sometimes it is straightforward age — older pilot assemblies wear out and fail to stay lit.
If your pilot light goes out, the furnace has a safety mechanism that stops gas from flowing to the burner. This prevents unburned gas from accumulating in the furnace, which would be dangerous. So a dead pilot light is annoying but not a safety hazard in itself.
Relighting a pilot light yourself
Many homeowners can relight a pilot light without calling a technician, and the furnace door usually has printed instructions. The basic steps are: turn the gas valve to "Pilot," hold down the ignition button (or a reset button), and use a long lighter or match to ignite the pilot opening while holding the button. Once the pilot is lit, you hold the button for 30 to 60 seconds to let the thermocouple heat up and sense the flame, then release it and turn the gas valve back to "On."
If the pilot will not stay lit after you release the button, or if it goes out again within a few hours, the thermocouple is likely failing and needs replacement. This is a job for a technician — the part is inexpensive (usually $15 to $50), but it requires opening the furnace and handling the gas line safely.
Do not attempt to relight the pilot if you smell gas in the house. Leave the house, call your gas company's emergency line, and wait for them to check for a leak. A strong gas smell means something is wrong with the gas supply or the furnace itself.
When to call a heating technician
Call a technician if the pilot light goes out repeatedly, if you cannot relight it after following the furnace instructions, or if you smell gas. Also call if the pilot light is lit but the main burner will not ignite — that usually means a problem with the ignition system or the gas valve, not something you can fix yourself.
If your furnace is more than 15 years old and the pilot light is going out often, it may be time to think about replacement. Pilot light furnaces are less efficient than modern electronic systems, and a furnace that is failing to light reliably is a sign that other parts are wearing out too. A technician can assess whether repair or replacement makes sense for your situation.
Pilot light furnaces versus electronic ignition: the main differences
A pilot light furnace burns a small flame continuously. When the thermostat calls for heat, that pilot flame ignites the main burner. The furnace runs until the house reaches the set temperature, then shuts down — but the pilot stays lit, waiting for the next call. This means the furnace is always using a small amount of gas, even when not actively heating.
An electronic ignition furnace has no standing flame. When the thermostat calls for heat, an electronic spark or a hot surface element ignites the burner. Once the burner is lit, the ignition system shuts off and the burner runs on its own. When the house reaches temperature, the burner shuts down completely, and nothing is burning until the next heating cycle. This saves gas and reduces wear on the system.
Electronic ignition furnaces are also more reliable in practice. A pilot light can blow out from a draft, a clogged opening, or a worn thermocouple. Electronic ignition has fewer moving parts and fewer things that can fail in that specific way. The trade-off is that electronic systems depend on electricity and a control board, so a power outage or electrical failure can prevent ignition — though most modern furnaces have battery backup for the ignition system.
Frequently Asked Questions
Can I convert my pilot light furnace to electronic ignition?
Some furnaces can be retrofitted with electronic ignition, but it is usually not worth the cost. A conversion kit can run $300 to $600 in parts and labor, and you are still using an old furnace with other aging components. Most homeowners find it more economical to replace the entire furnace when the pilot light system becomes unreliable.
Is a pilot light furnace dangerous?
No, a working pilot light furnace is safe. The thermocouple is a safety device that cuts off gas if the pilot goes out, preventing unburned gas from accumulating. However, if you smell gas or the pilot will not stay lit, have a technician inspect the furnace before using it again.
Why do some furnaces still use pilot lights?
Older furnaces were designed with pilot lights because electronic ignition was not yet available or reliable. Some commercial or industrial furnaces still use them because they are straightforward and do not depend on electricity. In residential heating, pilot lights are now considered outdated.
How much does it cost to replace a thermocouple?
A thermocouple part usually costs $15 to $50, but labor to install it runs $100 to $200 depending on your area and the technician. If your pilot light keeps going out, have the thermocouple tested before replacing it — sometimes the problem is a clogged pilot opening or a gas supply issue instead.
Will my furnace work if the power goes out?
A pilot light furnace will continue to run during a power outage because the pilot and burner do not need electricity to stay lit. An electronic ignition furnace will not ignite without power, though most modern models have a battery backup that keeps the ignition system working for a limited time. Check your furnace manual to see if yours has battery backup.