A pilot light is a small, continuously burning flame that ignites the main gas burners in a furnace or water heater when heating is needed. These flames consume 400 to 500 BTU per hour year-round, contributing 3 to 5 percent energy loss in older heating systems. Pilot lights have been largely replaced by electronic ignition systems in modern equipment.
Types and Operation
Standing pilot lights remain lit continuously, while intermittent pilots ignite only when needed. Standing pilots require manual lighting or reigniting after power outages or wind extinguishment. The small flame typically measures 0.5 to 1 inch in length and operates on a thermocouple or thermopile safety system that cuts gas supply if the pilot light goes out.
Maintenance Considerations
Pilot light maintenance includes periodic cleaning of the pilot burner to remove dust and debris affecting flame quality. A healthy pilot light appears blue with a yellow tip. Pilot lights in older furnaces cost 30 to 40 dollars to relight professionally, while systems using electronic ignition eliminate this recurring maintenance need and improve overall furnace efficiency for residential heating applications.