Most gas water heaters have a pilot light, but not all of them
A pilot light is a small, continuously burning flame that ignites the main burner when your water heater needs heat. Most traditional gas water heaters use one. However, some newer models use electronic ignition instead—a spark or hot surface that lights the burner without a standing flame. If your water heater is more than 10 to 15 years old, it almost certainly has a pilot light. If it's newer, check the label on the tank or your manual to be sure.
Electric water heaters don't have pilot lights at all—they use heating elements powered by electricity. Tankless water heaters (whether gas or electric) also typically use electronic ignition rather than a pilot light. The type you have depends on what fuel your home uses and when the unit was installed.
Key Takeaways
- Traditional gas water heaters use a pilot light—a small flame that stays lit to ignite the main burner when heat is needed.
- Newer gas water heaters often use electronic ignition (spark or hot surface) instead of a pilot light, which is more energy-efficient.
- Electric water heaters and tankless models do not have pilot lights.
- If your pilot light goes out, you can usually relight it yourself by following the instructions on the tank, but a professional should handle it if you smell gas.
How a pilot light works in a gas water heater
The pilot light is a small flame that burns continuously inside the combustion chamber of your water heater. It sits near the main burner. When a thermostat inside the tank senses the water temperature has dropped below the set point, it opens a gas valve. The pilot light ignites the gas flowing to the main burner, which heats the water. Once the water reaches the target temperature, the thermostat closes the valve and the main burner shuts off—but the pilot light stays on, waiting for the next cycle.
This design has been standard for decades because it is reliable and inexpensive to manufacture. The downside is that the pilot light burns fuel continuously, even when you are not using hot water, which wastes energy. That is why manufacturers began switching to electronic ignition systems in the 1990s and 2000s.
The difference between pilot lights and electronic ignition
An electronic ignition system does not keep a flame burning all the time. Instead, when the thermostat calls for heat, the system produces a spark or heats a surface to ignite the main burner. Once the burner is lit, the spark or hot surface shuts off. When the water reaches temperature, the burner closes and nothing burns until the next cycle.
Electronic ignition is more energy-efficient because it does not waste fuel on a standing pilot flame. However, it requires electricity to operate the spark or heating element, so your water heater needs either a battery backup or a direct electrical connection. Some older homes with gas-only service may not have wired power near the water heater, which is why many still use pilot lights.
If you are replacing an old water heater and want to upgrade to electronic ignition, an electrician can run a line to the unit if one does not already exist. The cost varies by distance and local rates, but it is usually a one-time expense that pays for itself over time through lower gas bills.
When a pilot light goes out and how to relight it
A pilot light can go out for several reasons: a draft blowing it out, a faulty thermocouple (the sensor that keeps the valve open), sediment buildup blocking the flame, or straightforward age. If your pilot light is out, the main burner will not light and your water heater will not heat water.
Most water heaters have relighting instructions printed on a label near the pilot assembly or inside the access panel. The basic steps are: turn the gas knob to "Off," wait a few minutes for gas to clear, turn it to "Pilot," hold down the ignition button (usually red or black) while holding a lit match or lighter to the pilot opening, and once it lights, release the button and turn the knob to "On." If the pilot stays lit after you release the button, you are done. If it goes out again, the thermocouple may be failing and you should call a professional.
If you smell gas at any point, do not attempt to relight the pilot yourself. Turn off the gas at the tank, leave the area, and call your gas company or a licensed plumber. A gas leak is a safety hazard.
Signs your pilot light needs attention
A healthy pilot light is a steady blue flame about the size of a pea. If the flame is yellow or orange, the burner may be dirty or the air-to-gas ratio may be off. If the flame is very small or flickers constantly, the thermocouple may be wearing out. Any of these signs mean the pilot light is not working as it should.
If your water heater cycles on and off frequently but never reaches the set temperature, or if it takes much longer than usual to heat water, a weak or failing pilot light could be the cause. In some cases, cleaning the pilot opening with a thin wire or needle can restore a steady flame. However, if relighting does not work or the flame will not stay lit, the thermocouple or gas valve likely needs replacement—a job for a professional.
When to call a professional for pilot light problems
You can safely relight a pilot light yourself if you follow the instructions on your tank and do not smell gas. However, call a plumber or your gas company if the pilot light will not stay lit after you relight it, if you smell gas, if the flame is discolored, or if you are uncomfortable working with the ignition system.
A professional can test the thermocouple, clean the pilot opening, adjust the gas pressure, or replace worn parts. Thermocouple replacement typically costs between $150 and $300, depending on your location and the plumber's rates. If the gas valve itself is failing, replacement is more expensive—usually $300 to $600—but still far less than replacing the entire water heater.
Water heaters without pilot lights
If you have an electric water heater, there is no pilot light to worry about. Electric units use heating elements submerged in the tank that turn on and off based on the thermostat. They are simpler in some ways because there is no combustion, no gas line, and no ignition system to maintain.
Tankless water heaters (also called on-demand units) heat water as it flows through the unit rather than storing it in a tank. Most modern tankless models use electronic ignition, so they also have no pilot light. Some older tankless units do have pilot lights, but they are rare in homes built in the last 15 years.
Frequently Asked Questions
Can a pilot light go out on its own?
Yes. A draft from an open door or window, a faulty thermocouple, sediment blocking the flame, or straightforward age can cause a pilot light to go out. If it happens once, relighting it usually solves the problem. If it goes out repeatedly, the thermocouple or gas valve likely needs professional attention.
Does a pilot light use a lot of gas?
A pilot light uses a small but continuous amount of gas—roughly 400 to 600 BTU per hour, depending on the model. Over a year, this adds up to noticeable energy waste, which is why newer water heaters use electronic ignition instead. The difference in your gas bill can be $10 to $20 per month.
What does a yellow pilot light flame mean?
A yellow or orange flame usually means the burner is not getting enough air or is dirty. This can reduce heating efficiency and may produce carbon monoxide. Clean the pilot opening with a thin wire, or call a professional if the flame does not turn blue after cleaning.
Can I convert my pilot light water heater to electronic ignition?
You cannot retrofit an existing pilot light system to electronic ignition—the burner assembly and gas valve are different. However, when you replace the water heater, you can choose a model with electronic ignition. An electrician will need to run power to the unit if a line does not already exist.
Is it safe to relight a pilot light myself?
Yes, if you follow the instructions on your tank and do not smell gas. If you smell gas, do not attempt to relight it—turn off the gas and call your gas company. If the pilot light will not stay lit after you relight it, stop trying and call a professional.