How Long Do Tankless Water Heaters Last?

Last updated on February 3, 2026

Quick Answer

The average life expectancy of a tankless water heater falls anywhere between 15 and 20 years, and often longer with regular maintenance. Gas models have a higher lifespan than their electric counterparts, simply because they don’t cycle on and off as often. Increasing the lifespan of your instantaneous water heater involves proper use and good care.

Have you ever stepped into a bathroom expecting a warm shower, only to be greeted by ice-cold water? If that’s so, you should definitely consider installing a tankless hot water system.

Unlike the storage tank hot water system, tankless heats water the moment you need it, so you will never again have to deal with those uncomfortable cold showers.

However, before investing in an on-demand water heater, you should first of all ask yourself, “How many years does a tankless water heater last?”

Finding an answer to this question helps because you aren’t just buying an appliance; you are investing in your home and want to make sure it’s a worthwhile investment.

As already mentioned above, the expected average lifespan of a tankless water heater is 15 to 20 years. The exact duration depends on a number of reasons, as we are going to explore in this post.

Why do Tankless Water Heaters Have a Longer Lifespan?

This is where the design makes a difference.

The typical life expectancy of tankless water heaters is higher because nothing is stored. No tank full of hot water sitting there all day. No constant pressure on metal walls. And no slow internal rusting.

A tankless unit stays idle until you turn on a tap. Then it heats water as it flows through. When the tap closes, it shuts down again.

There is less standing water. Less heat stress. And fewer things are wearing out slowly in the background.

That’s why these systems tend to last longer in the first place.

What Affects the Lifespan of a Tankless Water Heater?

Even good systems can wear out early if conditions aren’t right.

Here are some of the things that can lower the typical lifespan of a tankless water heater

Water quality – Hard water causes mineral buildup inside the heat exchanger, and this affects the overall performance of the system.
Usage habits – Large households push the system harder. Working harder puts more components under constant stress, leading to wear and tear.
Installation quality – Poor installations, like improper piping, bad ventilation, or improper electrical or gas connections, force the system to work outside its design limits, leading to early failure.
Fuel type – Gas units often edge out electric ones. This is because electric heaters rely on high-load heating elements that wear out faster, while gas systems spread heat more evenly and place less constant strain on internal components.
Maintenance – Lack of regular maintenance significantly reduces lifespan. Without periodic flushing and cleaning, mineral buildup restricts heat transfer, causes overheating, and puts extra strain on internal parts, especially in hard-water areas.

If you’ve ever wondered why two identical heaters age differently, this is usually why.

How to Make a Tankless Water Heater Last Longer?

If you want your unit to reach the upper end of its lifespan, focus on a few key habits.

🟩 Maintenance

Wondering how maintenance impacts tankless water heater lifespan? Regular flushing stops mineral buildup from settling inside the system. When that buildup is left alone, heat gets trapped, and parts work harder than they should. Over time, that extra strain shortens the heater’s life.

🟩 Filter cleaning

Tankless heaters depend on a steady water flow. When filters get dirty, the unit has to work harder to keep up. That doesn’t cause immediate failure, but it does increase wear on internal components over time.

🟩 Stable water pressure

These systems are designed to run within a specific pressure range. Ongoing pressure spikes or drops put stress on valves and sensors. Even if everything still works, that stress slowly reduces how long the heater will last.

🟩 Professional inspections

A yearly inspection helps catch small problems early. Things like loose connections or early scale buildup are easier to fix before they cause lasting damage. Skipping checks often leads to bigger issues later on.

🟩 Water quality control

Hard water speeds up mineral buildup inside the heater. A water softener helps reduce that buildup before it reaches the system. Over time, this can make a noticeable difference in how long the heater lasts.

When Should I Replace My Tankless Water Heater?

The question “how often do tankless water heaters need replacing?” usually comes from frustration or caution.

In most homes, tankless systems don’t need replacing for 15 to 20 years. That’s why many people never replace one at all during their time in a house.

If you’re replacing one sooner, it’s often due to skipped maintenance, poor installation, or extremely hard water.

Usually, you should replace your instantaneous water heater when:

The unit is over 20 years old
Repairs become frequent
Temperature swings don’t stop
Error codes keep returning

Replacing before full failure avoids cold showers and emergency call-outs. It also lets you upgrade efficiency instead of scrambling.

What is the Lifespan of a Tankless Water Heater Compared to a Storage Tank?

Here’s the simple breakdown of tank vs tankless water heater longevity:

Storage tank heaters: 10–15 years
Tankless water heaters: 15–20+ years

The difference comes down to corrosion and prolonged exposure to constant heat. Tanks deal with both. Tankless systems largely avoid them.

Quick recap

What is the lifespan of a tankless water heater? About 15–20 years
How many years does a tankless water heater last? Often longer with maintenance
Average lifespan of a tankless water heater: Roughly double that of some tank systems
Typical life expectancy of tankless water heaters: Extended by design
How maintenance impacts tankless water heater lifespan: More than any other factor

Final Thought

Conclusion

Tankless water heaters are built for longevity, but their lifespan isn’t automatic. While most systems are designed to last 15 to 20 years or more, how long yours actually lasts depends on how it’s installed, how it’s used, and how well it’s cared for over time.

Regular maintenance, stable water pressure, and good water quality make a real difference in the typical lifespan of a tankless water heater. Skip them, and even the best unit can wear out early.