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Kenmore Water Heater Age: How to Decode the Serial Number

A.O. Smith

Also works for A.O. Smith-built labels: State, Reliance, American, Whirlpool, U.S. Craftmaster, Kenmore, GSW and John Wood.

How Old Is Your Kenmore Water Heater?

Here is the surprise most Kenmore owners never learn: Sears never manufactured a single water heater. Kenmore is a retail badge, not a factory. Sears bought its water heaters from established manufacturers and sold them under the Kenmore name — and over the decades, more than one company held that contract.

Who Actually Made Your Kenmore

According to industry references, Kenmore water heaters were built and rebranded by a variety of companies, including A.O. Smith, Rheem, State Industries, and Whirlpool. The A.O. Smith family is the most common source — State Industries (acquired by A.O. Smith in 2008) was a long-time Kenmore supplier, and American Water Heater is also part of the A.O. Smith group. Rheem and Whirlpool built certain lines as well. The exact year ranges for each supplier are not publicly documented, so the reliable way to identify your unit's maker is the serial number format.

How to Tell: Serial Format Differences

Check the first characters of your serial against these documented patterns:

  • A.O. Smith style — a letter followed by digits, e.g. A03307353 or J06A059461. The 2nd and 3rd digits are the year; the leading letter encodes the month.
  • Rheem style — all digits, e.g. 800423049. The 1st and 2nd digits are the year, the 3rd and 4th the week — so this one reads as week 4 of 1980.
  • State / Whirlpool style — digits, sometimes with a letter or space inside, e.g. 1210A002243 or S1318 F000046. Again the year and week sit in the first four digits.

Try This Decoder First

Because the majority of Kenmore tanks came from the A.O. Smith family, start with the decoder above. If it can not make sense of your serial — especially if your serial is all digits and opens with a plausible year-week pair — your unit is probably Rheem-built, so try our Rheem serial number decoder next.

Where to Find the Rating Plate

Look for the rating plate (data plate) on the side of the tank — a silver or white sticker, usually in the upper half, listing the model and serial numbers together. Kenmore model numbers typically carry a three-digit Sears prefix followed by a dot (e.g. 153.xxxxx), which also points to the original supplier.

Why the Age Matters

  • Lifespan. Tank water heaters average 8–12 years. Since Kenmore-branded units are no longer being made, yours is almost certainly deep into — or past — that window.
  • Failure risk. Internal corrosion makes tank rupture and a flooded floor much more likely in an aging unit.
  • Replacement planning. Knowing the exact manufacture date lets you replace on your schedule, not during an emergency.

Sources

Manufacturer history and serial formats verified against the Building Intelligence Center Kenmore water heater dating guide and the InterNACHI water heater dating chart. State Industries' acquisition by A.O. Smith per Working RE's water heater dating overview.

Frequently asked questions

Who actually makes Kenmore water heaters?
No one at Sears ever did — Kenmore has always been a retail brand. Sears sourced its water heaters from established manufacturers, most commonly the A.O. Smith family (including American Water Heater and State Industries), plus Rheem and Whirlpool on some lines. The Kenmore brand itself is now owned by Transformco.
How can I tell which company made my Kenmore water heater?
The serial number format is the giveaway. A.O. Smith-style serials often start with a letter followed by digits (like A03307353), with the year in the 2nd and 3rd digits. Rheem-style serials are all digits with the year first (like 800423049 for week 4 of 1980). State and Whirlpool styles put the year and week in the first four digits (like 1210A002243).
Where is the serial number on a Kenmore water heater?
On the rating plate — a sticker on the side of the tank, usually in the upper half. It lists the model number and serial number together. Sears model numbers typically start with a three-digit prefix followed by a dot (for example, 153.xxxxx), which also hints at the original supplier.
What if the decoder on this page can not read my serial?
This page runs the A.O. Smith decoder, which covers the majority of Kenmore units. If your serial is all digits and starts with a plausible year-week pair, your unit may be Rheem-built — try the Rheem decoder at /rheem/serial-number-lookup/ instead.
Are Kenmore water heaters still being made?
New Kenmore water heaters appear to be discontinued. After Sears Holdings filed for bankruptcy in 2018, the Kenmore brand passed to Transformco, and dedicated Kenmore water heater listings have largely disappeared. That makes decoding the age of an existing unit even more useful — any Kenmore tank still in service is likely approaching or past the typical 8–12 year lifespan.