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Kilowatt Heating, Air Conditioning and Electrical Blog

What Happened to Pilot Lights in Furnaces?


This is a question people sometimes ask when they look at the furnaces professionals currently install in homes, or when they see a new furnace in a home. Most current homeowners likely grew up in houses with furnaces that used pilot lights, or owned a furnace with a pilot light. Yet the pilot light is becoming an endangered species in home heating. 

What happened? Why has the standing pilot light been extinguished, and what took its place?

This isn’t just trivia questions. You can understand a good deal about your furnace’s operation and how it uses energy when you know a bit more about the fate of the standing pilot light.

The Job of the Standing Pilot Light

We want to point out that when we say pilot light we’re specifically referring to standing pilot lights, i.e. a pilot light that continues to burn throughout the winter season. There are other types of pilot lights, and we’ll talk about one later in this post. 

The standing pilot light started to appear in gas furnaces in the 1920s, and it was a great invention at the time. People used to need to manually light their furnaces whenever they needed heat. The pilot light took care of it automatically: as soon as gas started to flow to the burners, the pilot light would ignite them. (A special part called the thermocouple would detect if the flames actually lit and would shut off the gas if they didn’t—a key safety feature.)

All well and good… but progress marches on, and pilot lights have two drawbacks that would eventually make them obsolete when new technology arrived.

First, a pilot light that burns all through the winter is wasting energy. The furnace doesn’t run 24/7, but a standing pilot light does. Although the gas use may seem small, it accumulates over the season and can account for an additional 432,000 BTUs burned each month. Eliminating pilot lights is one of the reasons newer furnaces have much better energy efficiency.

Second, pilot lights have reliability troubles. Anyone who has used a gas furnace with a standing pilot light can tell stories about when the pilot light blew out, and how getting it relit and the furnace back working was a complete pain. It’s an aggravation nobody needs.

Electronic Furnace Ignition

Electronic ignition systems began to replace pilot lights in gas furnaces starting in the 1980s, and almost all residential furnaces constructed since 2010 use them. There are two types. Less common is the intermittent pilot, which is a pilot light that ignites from an electric spark and only remains burning long enough to light the burners and then shut off. 

Most furnaces use a hot surface ignitor, in which electrical current is sent through the ignitor to turn it hot (similar to how a filament in a lightbulb becomes hot). The hot surface then ignited the burners and shuts off. 

Although electronic ignition systems are more reliable than standing pilot lights, you may still need furnace repair in Studio City, CA, for yours at some point. Trust our team to handle the work.

Call our certified service technicians 24/7 for exceptional customer service! Kilowatt Heating, Air Conditioning and Electrical serves Los Angeles and the San Fernando Valley.

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