Most tankless water heaters do not have a pilot light
Tankless water heaters work differently from tank models, and most do not use a pilot light at all. Instead, they rely on an electronic ignition system that lights the burner only when you turn on hot water. When you open a faucet, a flow sensor detects the water movement, and an electric spark or hot surface igniter fires up the heating element. Once you close the faucet, the burner shuts off when ready.
This is one of the main reasons tankless models are more energy-efficient than tank heaters. A traditional tank heater keeps a pilot light burning 24/7 to maintain a small flame, even when nobody is using hot water. A tankless heater only burns fuel when it is actively heating water, so you are not paying to keep a flame alive all night.
A very small number of older or specialty tankless models do have pilot lights, but this is rare in modern units sold in North America. If you own an older propane tankless heater or a model designed for off-grid use, check your manual to confirm which ignition type yours uses.
Key Takeaways
- Most tankless water heaters use electronic ignition (a spark or hot surface igniter) instead of a standing pilot light.
- The ignition system only activates when water flow is detected, so the burner does not run continuously.
- Electronic ignition is one reason tankless heaters use less energy than tank models with pilot lights.
- Older or specialty tankless models may have pilot lights, so check your manual if you are unsure which type you have.
- Electronic ignition systems require electricity to work, even on gas tankless heaters.
How electronic ignition works in tankless heaters
When you turn on a hot water tap, water enters the tankless heater and passes over a flow sensor. This sensor sends a signal to the control board, which then triggers the ignition system. Most modern units use one of two methods: a spark igniter (which creates a small electrical spark to light the gas) or a hot surface igniter (a ceramic element that heats up and ignites the gas when electricity passes through it).
Once the burner lights, it stays on as long as water is flowing through the unit. The moment you close the faucet, the flow stops, the sensor detects no water movement, and the burner shuts off. This on-demand approach means the heater only consumes fuel when it is actually heating water, unlike a tank heater that maintains a pilot flame constantly.
The ignition system is controlled by a circuit board inside the heater. This board monitors water flow, temperature, and gas pressure to may support safe operation. If the igniter fails to light the gas, the board will shut down the system and display an error code on the control panel.
Why tankless heaters switched away from pilot lights
Manufacturers moved to electronic ignition because it saves energy and money. A pilot light on a tank heater burns continuously, consuming gas even when nobody is using hot water. Over a year, that adds up. A tankless heater with electronic ignition only ignites when needed, cutting fuel waste significantly.
Electronic ignition is also more reliable and safer. A pilot light can blow out from drafts, vibration, or age, leaving the heater unable to light the main burner. An electronic igniter has fewer moving parts and is less likely to fail. If it does fail, the control board detects the problem and prevents gas from flowing, reducing the risk of a gas leak.
The trade-off is that electronic ignition requires electricity. Even gas tankless heaters need power to run the ignition system, control board, and flow sensor. This means a power outage will prevent the heater from working, whereas some older tank heaters with pilot lights can still produce hot water during an outage (though the burner will not light automatically).
What happens if the igniter fails
If the spark igniter or hot surface igniter stops working, your tankless heater will not light. You will turn on a hot water tap and get only cold water. The control board will detect that the igniter failed to light the gas and will shut down the system to prevent gas from accumulating.
Most units display an error code on the digital display when this happens. The code tells you what went wrong — in this case, usually something like "ignition failure" or "no flame detected." Write down the code and check your manual or contact a technician. Igniter replacement typically costs between $150 and $300 in parts and labor, depending on the model and your location.
Do not attempt to repair the igniter yourself unless you have experience with gas appliances. The ignition system involves both electrical and gas components, and mistakes can be dangerous. A licensed technician can safely diagnose and replace the part.
Electricity requirements for tankless heaters
Because tankless heaters rely on electronic ignition, they need a reliable power supply. Most units require either 110 volts or 240 volts, depending on the model and size. Check your heater's manual or the nameplate on the unit to see what voltage it needs.
If your home loses power, the heater will not work. Some people install a battery backup or small generator to keep the ignition system running during outages, but this is not standard. If you live in an area with frequent power outages, ask your installer whether a backup power option is available for your model.
The electrical demand is usually modest — most tankless heaters draw only a few amps for the ignition and control systems. However, some larger electric tankless heaters (which heat water entirely with electricity rather than gas) require significant power and may need a dedicated circuit.
Maintenance differences between pilot lights and electronic ignition
Electronic ignition systems require less maintenance than pilot lights. You do not need to clean the igniter regularly or worry about it blowing out. However, you should still have your tankless heater serviced annually by a professional. During service, the technician will inspect the igniter, clean the heat exchanger, and check that all sensors are working correctly.
If your heater is in a dusty or corrosive environment (such as a garage near salt air or a workshop with metal dust), the igniter may accumulate debris and fail sooner. Regular maintenance helps catch these problems early. Descaling the heat exchanger is also important in hard-water areas, as mineral buildup can reduce efficiency and eventually damage the unit.
Keep the area around your heater clean and free of obstructions. The unit needs good airflow to operate safely, and dust or debris can clog the air intake and damage the igniter.
Frequently Asked Questions
Can I convert a tankless heater with electronic ignition to use a pilot light?
No. The two systems are fundamentally different and require different burner designs and control boards. Conversion is not practical or safe. If you prefer a pilot light system, you would need to replace the entire heater with an older model, which is not recommended because modern electronic ignition is more efficient and reliable.
What should I do if my tankless heater will not light during a power outage?
The heater cannot light without electricity for the ignition system. If you need hot water during an outage, you have a few options: use a portable propane heater (with proper ventilation), boil water on a gas stove if you have one, or wait for power to be restored. Some people install a battery backup system, but this is an additional investment.
Is the spark igniter the same as a pilot light?
No. A pilot light is a small flame that burns continuously. A spark igniter is an electrical component that creates a spark to light the main burner only when needed. The spark igniter uses electricity and has no flame of its own — it straightforward ignites the gas.
How long do electronic igniters last?
Most electronic igniters last 5 to 10 years with proper maintenance. The lifespan depends on water quality, how often the heater is used, and whether the unit is serviced regularly. Hard water and frequent use can shorten the igniter's life. If your heater is older and the igniter fails, replacement is usually the most practical solution.
Do all gas tankless heaters use electronic ignition?
Most modern gas tankless heaters sold in the United States use electronic ignition. Some older models and specialty units designed for off-grid or emergency use may have pilot lights. Check your heater's manual or the manufacturer's website to confirm which type you have.