The term “pilot light” is often associated with traditional gas furnaces, but some gas-fired tankless water heaters still rely on a standing pilot or a pilot-like ignition method. This article explains how pilot lights work in tankless models, the benefits and drawbacks, safety considerations, and guidance for choosing and maintaining a unit in American homes. Understanding these details helps homeowners make informed decisions about efficiency, cost, and reliability.

How A Pilot Light Works In Tankless Water Heaters

Most modern gas tankless water heaters use an electronic ignition system to ignite gas on demand, rather than a continuous standing pilot. A standing pilot is a small continuously burning flame that preheats the burner, while electronic ignition uses spark or hot-surface ignition to light the burner only when hot water is demanded. Some older or specialty models may still incorporate a standing pilot, but it is less common in today’s high-efficiency designs. In models with a pilot, the flame is monitored by a flame sensor to ensure safe operation.

Pros And Cons Of Pilot-Driven Systems

Pros: Some tankless units with a standing pilot can offer rapid ignition in environments with low inlet gas pressure, and may provide simple troubleshooting for technicians familiar with pilot systems. They can be compatible with certain older gas lines without upgrading ignition control boards.
Cons: Standing pilots consume gas continuously, reducing overall efficiency and increasing operating costs. They also require more routine maintenance to ensure the pilot and flame sensor stay clean, and they may have higher standby heat losses compared with electronic ignition systems.

Safety Considerations

Safety remains paramount with any gas appliance. For units with a standing pilot, routine inspection of the pilot flame to ensure it burns cleanly is important, along with checking the flame sensor and thermocouple for proper operation. Venting must be unobstructed and properly pitched to prevent backdrafts. If a pilot flame goes out, a failed ignition sequence or gas leak risk can occur, so many modern tankless heaters rely on electronic ignition to minimize these risks. For homeowners, consulting a licensed plumber or gas technician for installation and maintenance is strongly recommended.

Efficiency, Operating Costs, And Monitoring

Tankless water heaters are typically praised for high efficiency, with many models achieving Energy Factor (EF) ratings well above traditional tank heaters. However, keeping a standing pilot adds a baseline energy draw even when hot water demand is low. In cold climates or homes with frequent hot water needs, the impact can be noticeable over time. When evaluating total cost of ownership, homeowners should compare the annual gas consumption of a unit with a standing pilot versus an electronic ignition model. For most households, modern electronic ignition tankless models deliver lower operating costs and reduced standby loss.

Maintenance And Troubleshooting

Regular maintenance helps ensure reliable performance. For pilot-based systems, maintenance includes periodic inspection of the pilot flame for proper size and cleanliness, cleaning or replacing the flame sensor, and verifying venting integrity. Electronic-ignition tankless models still require annual service checks to clean burners, inspect gas line connections, and ensure proper combustion. Common issues include err codes related to ignition failure, gas supply problems, and vent blockages. Homeowners should follow the manufacturer’s service schedule and contact an HVAC professional for any ignition or gas-related concerns.

Choosing A Model: Key Considerations For U.S. Homes

Ignition Type: Prefer electronic ignition for higher efficiency and lower standby gas usage, unless a specific application requires a standing pilot.
Capacity And Flow Rate: Select a unit rated for the peak household hot-water demand, measured in gallons per minute (GPM). Consider simultaneous use like showers and appliances.
Vent And Gas Line Compatibility: Confirm venting requirements and gas pressure tolerance for the chosen model. Some installations need upgrading of gas lines or vent stacks.
Efficiency Rating: Look for models with high uniform energy factors (UEF or EF) and compliance with local energy standards.
Warranty And Service Network: Choose brands with solid warranties and a nationwide service network for easier maintenance and repairs.

Installation Considerations

Professional installation ensures safe gas connections, proper venting, and correct clearance from combustibles. Tankless water heaters require adequate gas supply, vent sizing, and often a dedicated electrical circuit for electronic ignitions. While some homes can replace an old tankless unit with a similar model, others may need upgrades to meet current codes and efficiency standards. Before purchasing, homeowners should obtain a precise installation plan and a cost estimate that includes potential ducting or venting work, gas line upgrades, and permitted electrical work.

Common Myths About Pilot Lights And Tankless Models

Myth: Pilot lights are always inefficient. Fact: In many modern systems, pilot lights are absent or minimized through electronic ignition to maximize efficiency.
Myth: All tankless heaters use standing pilots. Fact: Most contemporary tankless water heaters use electronic ignition, with standing pilots mainly in older or specialized models.
Myth: A pilot light means constant hot water. Fact: Tankless systems heat on demand, regardless of ignition method, but standby losses can vary.

Maintenance Schedule At A Glance

Inspect the unit annually for gas connections, venting, and mounting stability.
Clean burners and inspect the flame sensor if the unit uses a standing pilot.
Test ignition operation and verify proper flame characteristics during service.
Schedule professional servicing every 1–2 years, depending on usage and manufacturer guidelines.