Most tankless water heaters do not have a pilot light

Tankless water heaters use electronic ignition instead of a standing pilot flame. When you turn on hot water, a sensor detects the flow, and an electric spark or hot surface igniter lights the burner. The flame shuts off the moment you stop using hot water. This is the opposite of a tank heater, which keeps a pilot light burning 24/7 to ignite the main burner whenever the water temperature drops.

Because tankless models only ignite when needed, they waste far less gas than a system that maintains a constant pilot flame. However, this also means they depend on electricity to start—even gas tankless heaters need power for the ignition system and control board.

Key Takeaways

  • Tankless water heaters use electronic ignition (spark or hot surface) instead of a pilot light that burns continuously.
  • The ignition system activates only when hot water is running, then shuts off when ready after you stop using it.
  • Gas tankless heaters still require electricity to power the ignition system and controls, even though they burn gas for heat.
  • If your tankless heater won't ignite, the problem is usually a dead battery in the ignition module, a tripped breaker, or a blocked sensor—not a pilot light issue.

How electronic ignition works in tankless heaters

When you open a hot water tap, water flows through the heater's heat exchanger. A flow sensor detects this movement and sends a signal to the control board. The board then triggers the ignition system—either a spark electrode (similar to a gas stove igniter) or a hot surface igniter (a ceramic element that glows red-hot). Once the burner lights, the flame heats the water as it passes through the exchanger.

The moment you close the tap and water stops flowing, the sensor signals the board to shut off the gas valve and the ignition system. No flame burns between uses. This on-demand design is why tankless heaters are more energy-efficient than tank models, which heat and reheat the same water all day and night.

Why tankless heaters need electricity despite burning gas

A gas tankless heater requires electricity to operate its ignition system, control board, and sensors. Most units run on either a standard 120-volt household outlet or a dedicated 240-volt circuit, depending on the model. If the power goes out, the heater will not ignite, even if you have gas flowing to it.

Some tankless heaters have a battery backup for the ignition system, which allows them to light during a power outage. Check your heater's manual to see whether yours has this feature. If it does, you will need to replace the battery (usually a 9-volt or AA) every few years to keep the backup functional.

What to check if your tankless heater won't ignite

If your tankless heater is not producing hot water, the problem is rarely a pilot light—because there is no pilot light. Instead, check these common causes in order:

  • Power supply: Make sure the heater is plugged in and the circuit breaker has not tripped. Look for a reset button on the control panel and press it if the breaker is off.
  • Ignition module battery: If your heater has a battery backup, the battery may be dead. Open the access panel and check the battery connections; replace the battery if it is corroded or old.
  • Flow sensor: Mineral buildup or debris can block the sensor and prevent ignition. If you live in a hard-water area, the sensor may need cleaning or descaling.
  • Gas valve: Confirm that the gas supply is on at the heater and at your meter. If you smell gas but the heater won't light, the gas valve may be stuck.
  • Ignition electrode or element: A cracked spark electrode or burned-out hot surface igniter will prevent the burner from lighting. These parts can be replaced, but the repair usually requires a technician.

If none of these steps restore ignition, contact a licensed technician. Tankless heater repairs often involve parts that require special tools or training to replace safely.

Comparing pilot light systems to electronic ignition

Tank water heaters with a pilot light burn a small flame continuously, using a small amount of gas even when you are not using hot water. The pilot light is always ready to ignite the main burner. If the pilot light goes out—due to a draft, a faulty thermocouple, or a clogged orifice—the main burner will not light, and you have no hot water until you relight it.

Tankless heaters with electronic ignition have no standing flame, so there is nothing to blow out or go out on its own. The ignition happens only when water flows, which means the system is more efficient but also more dependent on electricity and sensors. Both systems are reliable when maintained, but they fail in different ways.

Maintenance differences between the two systems

A tank heater with a pilot light requires occasional cleaning of the pilot orifice (the small opening where gas flows to the pilot) and inspection of the thermocouple (the safety device that shuts off gas if the pilot goes out). These are straightforward tasks that many homeowners can do themselves.

A tankless heater with electronic ignition requires descaling to remove mineral buildup from the heat exchanger and sensors, especially in hard-water areas. This is usually a professional job, though some manufacturers sell descaling kits for homeowners. You should also check battery connections annually if your heater has a battery backup. Neither system requires constant attention, but both benefit from annual inspection by a technician.

Frequently Asked Questions

Can I manually light a tankless water heater if the ignition fails?

No. Tankless heaters are designed to ignite electronically only. There is no pilot light to light by hand, and attempting to ignite the burner manually is unsafe. If the ignition system fails, the heater will not produce hot water until the problem is repaired.

Do all tankless water heaters require electricity?

Yes, all modern tankless heaters—whether gas or electric—require electricity to operate. Gas tankless heaters use electricity for ignition, controls, and sensors. Electric tankless heaters obviously need power for heating. If you want a heater that works during a power outage, look for a model with a battery backup for the ignition system.

What happens to a tankless heater during a power outage?

Without power, a gas tankless heater will not ignite, so you will have no hot water. An electric tankless heater will not work at all. If your heater has a battery backup, the ignition system may still work, but you should check your manual to confirm. Once power is restored, the heater should resume normal operation.

Is a tankless heater more reliable than a tank heater with a pilot light?

Both are reliable, but they fail differently. Tank heaters with pilot lights can lose the pilot flame due to drafts or a faulty thermocouple. Tankless heaters depend on electricity and sensors, so they fail if the power goes out or the sensor gets blocked. Neither is inherently more reliable; it depends on your home's conditions and maintenance habits.

How often should I have my tankless heater serviced?

Most manufacturers recommend annual inspection and descaling, especially in hard-water areas. If you have a battery backup, check the battery connections once a year. Regular maintenance prevents mineral buildup and keeps the ignition system working properly. A technician can identify problems before they cause a breakdown.