How long does a water heater last?

Tank models typically last about 8 to 12 years, according to A. O. Smith and Lennox. Tankless models typically last 15 to 20 years, according to A. O. Smith.

Is the manufacture date the same as the install date?

Not always. The serial number tells you when the heater was made; it may have been installed later.

How old is my water heater?

The quickest way to find out is the serial number on the rating label: for the brands we decode, it includes the manufacture date. Here’s where to look, and how long water heaters usually last.

Find the rating label

Tank water heaters: The rating label is on the side of the tank: near the gas control valve on gas models, or above the upper heating-element cover on electric models.

Tankless water heaters: The rating label is on the side of the unit's cabinet. Some models also show it behind the front cover.

Decode the serial number

Enter the serial number below. We decode Rheem, Ruud, A.O. Smith, State, Bradford White, Rinnai and Navien serial numbers using documented formats. If a serial doesn’t match a documented format, we say so instead of guessing.

The date is when the heater was made. It may have been installed later.

How long water heaters last

Tank water heaters: A. O. Smith says “the average life expectancy of a water heater is about 8 to 12 years”, and Lennox says “a typical tank water heater lasts between 8-12 years”. NAHB’s study gives about 10 years for gas or electric tanks, and Bradford White says its water heaters “can last 10 years or more” with professional installation and proper maintenance.

Tankless water heaters: A. O. Smith says they “typically last 15 to 20 years with proper care and maintenance”, and the U.S. Department of Energy estimates an average of about 20 years.

When age matters

A. O. Smith’s advice: “If your water heater is more than 10 years old, leaks around the base of the tank or operates erratically, it’s probably time to replace your water heater.” Age alone doesn’t tell you a heater’s condition, but it helps you plan ahead instead of waiting for a leak.

Decode your water heater’s serial number

Free, no account needed Photo scanning coming soon

Questions

Where is the serial number on a water heater?: The rating label is on the side of the tank: near the gas control valve on gas models, or above the upper heating-element cover on electric models. On tankless models, it’s on the side of the unit’s cabinet.
How long does a water heater last?: Tank models typically last about 8 to 12 years, according to A. O. Smith and Lennox. Tankless models typically last 15 to 20 years, according to A. O. Smith.
Is the manufacture date the same as the install date?: Not always. The serial number tells you when the heater was made; it may have been installed later.

Sources

Last updated 2026-09-29.