How long does a water heater last?

Tank water heaters: 10 to 15 years

A tank heater is a steel vessel with a glass lining and a sacrificial anode rod, a length of magnesium or aluminum that the water attacks first. While the rod lasts, the tank is protected. Once it is used up, the water starts on the steel, and the tank eventually seeps through its body. That leak has no repair.

Gas and electric tanks share that construction, and the Department of Energy's 10 to 15 year range covers both. What breaks along the way differs. A gas heater loses a thermocouple, a burner or a gas valve. An electric heater loses an element or a thermostat. Each of those is one part, and on a younger tank the part gets replaced, not the heater.

Tankless water heaters: more than 20 years

With no tank there is no standing water to rust a vessel from the inside, which is why the Department of Energy gives tankless units a longer life. The parts inside, such as the igniter, the sensors and the fan, can be replaced one at a time.

Scale is what shortens it. Hard water leaves minerals on the heat exchanger, and that costs efficiency first and the unit later. A yearly descale is the maintenance that gets a tankless unit to its full age. See tank or tankless if you are choosing between the two.

Does a bigger tank last longer?

No source we trust gives a lifespan by tank size, and size is not what wears a heater out. A 50 gallon tank and a 40 gallon tank of the same build age the same way. Size decides whether the last person in the shower gets hot water. When we replace a heater, we size the new one from how the house uses hot water, so the decision is about capacity, not age.

What shortens a water heater's life

• Sediment that is never flushed. It settles on the tank floor, makes the burner or lower element work through it and is what you hear rumbling.
• An anode rod nobody has checked. Once it is eaten away, the lining is next.
• Water pressure that runs too high. It strains the tank, the relief valve and every connection. A gauge on an outside tap tells you in a minute.
• Scale on a tankless heat exchanger in hard water, left from one year to the next.

Flushing the tank and checking the anode rod once a year is the maintenance that pushes a tank toward the long end. Our plumbing maintenance checklist puts it on the calendar.

How to tell how old your water heater is

Look at the label on the side of the tank or the unit. The manufacture date is printed on many of them. On others it is coded into the serial number, usually as a month and a year in the first few characters. If you cannot read it, photograph the whole label and send it with the form below, and we will read it for you.

What age means for repair or replace

Our rule of thumb on a tank: younger than eight with one failed part, it gets the part. Older than ten, we would rather you spend the money on the new heater, because the repair tends to buy months, not years. Seepage from the tank body means a new heater whatever the age. The full reasoning is in repair or replace a water heater, and what moves the price of a new one is in how much it costs to replace a water heater.

A puddle beside the heater does not settle it on its own. It may come from the drain valve at the bottom, a loose union on top or the pipe running down from the relief valve, and any of those is a part. We trace the water to its source before a new tank comes up.

Where these numbers come from

The 10 to 15 year range for tanks and the more than 20 years for tankless units are from the US Department of Energy's Energy Saver guide (2022 edition), read in November 2026. They are typical ranges, not a promise for any one heater. We found no primary source that gives separate figures for gas and electric tanks or for tank sizes, so this page does not print any.