Not all furnaces have pilot lights anymore
Modern furnaces are split between two ignition systems: those with a pilot light (a small, constantly burning flame) and those with electronic ignition (which lights the burner only when heat is needed). Most furnaces built after the 1990s use electronic ignition. Furnaces with pilot lights are still common in older homes, but they are becoming less frequent in new installations because electronic systems are more energy-efficient and reliable.
The type of ignition your furnace has depends on when it was manufactured and what your home's original installer chose. If you are unsure which system you have, you can look inside the furnace combustion chamber—a pilot light is visible as a small blue flame. If you see no flame and the furnace only ignites when the thermostat calls for heat, you have electronic ignition.
Key Takeaways
- Furnaces built before the 1990s typically have pilot lights; most newer furnaces use electronic ignition instead.
- A pilot light burns continuously and uses a small amount of gas year-round, while electronic ignition only uses gas when the furnace runs.
- You can identify which system you have by looking for a visible flame in the combustion chamber or checking your furnace's age and model number.
- Pilot light furnaces are less efficient but often cheaper to repair, while electronic ignition furnaces cost more to fix but save money on gas over time.
Why furnaces switched away from pilot lights
Pilot lights waste energy because they burn continuously, even during summer when you do not need heat. A pilot light uses roughly 5 to 15 percent of a furnace's total gas consumption just to stay lit. Electronic ignition systems eliminate this waste by igniting the burner only when the thermostat signals that heat is needed, then shutting off when the room reaches the set temperature.
Electronic ignition is also more reliable. Pilot lights can blow out from drafts, dust, or wear, leaving you without heat until you relight them. Electronic systems have fewer moving parts and fewer reasons to fail. Manufacturers began switching to electronic ignition in the 1980s and 1990s as energy codes tightened and homeowners became more cost-conscious about heating bills.
How to tell what ignition system your furnace has
The simplest way is to look at your furnace. Turn off the power at the breaker, wait a few seconds, then turn it back on. If you hear a clicking sound and see a small blue flame appear in the combustion chamber (the metal box where gas burns), you have electronic ignition. If you see a small blue flame that is always there, even when the furnace is not running, you have a pilot light.
You can also check your furnace's age. Look for a label on the side or back of the unit that shows the model number and manufacture date. Furnaces from the 1980s and earlier almost always have pilot lights. Furnaces from the 1990s onward are split, with many having electronic ignition but some still using pilots. Furnaces made after 2010 rarely have pilot lights unless they are specialty models.
If you cannot find the label or are uncomfortable opening the furnace, call a heating technician. They can tell you in seconds which system you have and explain what it means for maintenance and repair costs.
Pilot light furnaces: advantages and drawbacks
The main advantage of a pilot light furnace is cost. Pilot light systems are simpler mechanically, so repairs are often cheaper and easier. If the pilot goes out, you can usually relight it yourself by following the instructions on the furnace door—no technician needed. Replacement parts for pilot light systems are also less expensive than electronic ignition components.
The drawbacks are significant. Pilot lights waste gas and raise your heating bill. They can go out unexpectedly, leaving you without heat in the middle of winter. Pilot lights also produce a small amount of continuous combustion, which means slightly more wear on the furnace over time. If you have an older pilot light furnace, you may also face difficulty finding replacement parts as manufacturers phase them out.
Electronic ignition furnaces: efficiency and reliability
Electronic ignition furnaces save money on gas because they do not burn fuel when heat is not needed. Over a heating season, this can reduce your gas bill by 5 to 15 percent compared to a pilot light system. Electronic systems are also more reliable—there is no flame to blow out, and the ignition happens automatically every time the thermostat calls for heat.
The trade-off is repair cost. Electronic ignition components are more complex and more expensive to replace. If the ignition module fails, you may pay $300 to $600 for parts and labor, whereas a pilot light repair might cost $100 to $200. However, electronic systems fail less often, so over the life of the furnace, the total repair cost is often lower.
What to do if your pilot light keeps going out
If you have a pilot light furnace and the flame goes out frequently, the problem is usually one of three things: a dirty pilot orifice (the small opening where gas flows to the pilot), a weak thermocouple (the sensor that tells the furnace the pilot is lit), or a draft in the furnace area.
Start by relighting the pilot following the instructions on your furnace door. If it goes out again within a few days, try cleaning the pilot orifice with a thin wire or needle—turn off the gas first and let the furnace cool. If cleaning does not help, the thermocouple may be failing and needs replacement by a technician. If the furnace is in a drafty basement or garage, weatherstripping or a furnace cover can help protect the pilot from wind.
Replacing a pilot light furnace with electronic ignition
You cannot straightforward swap the ignition system on an existing furnace—the two systems require different burner designs and gas valves. However, you can replace an old pilot light furnace with a new electronic ignition furnace. A new furnace typically costs $3,000 to $8,000 installed, depending on size and efficiency rating, but will save money on gas over 15 to 20 years.
If your pilot light furnace is still working well, there is no urgent reason to replace it. Many homeowners keep pilot light furnaces running for decades. Replacement makes sense if the furnace is over 20 years old, failing frequently, or if your heating bills are noticeably high. A heating contractor can assess your furnace and tell you whether repair or replacement is the better choice for your situation.
Frequently Asked Questions
Can I convert my pilot light furnace to electronic ignition?
No, you cannot retrofit electronic ignition onto a pilot light furnace. The two systems require different burner assemblies and gas valves. If you want electronic ignition, you must replace the entire furnace. A technician can advise whether replacement or repair makes sense for your current unit.
Do all gas furnaces have pilot lights?
No. Most gas furnaces made after 1995 use electronic ignition. Pilot lights are found mainly in older furnaces, though some specialty models and high-efficiency furnaces may still use them. Check your furnace's manufacture date or look for a visible flame to determine which system you have.
Is a pilot light furnace safe?
Yes, pilot light furnaces are safe when working correctly. The pilot flame is contained in a sealed combustion chamber, and the furnace vents exhaust outside. However, if the pilot goes out and gas continues to flow without igniting, unburned gas can accumulate—which is why furnaces have safety shutoffs that stop gas flow if the pilot does not light within a set time.
How much does it cost to replace a thermocouple in a pilot light furnace?
A thermocouple replacement typically costs $150 to $300 including labor. The part itself is inexpensive (under $50), but the technician's time and service call make up most of the cost. If your pilot keeps going out, have a technician diagnose the problem before paying for a replacement.
Will a new furnace definitely have electronic ignition?
Almost certainly yes. New furnaces sold today are almost always electronic ignition because they meet modern energy codes and are more efficient. Pilot light furnaces are rarely manufactured anymore, though some specialty or commercial models may still use them. Ask your installer to confirm the ignition type when you get a quote.