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How old is my Kenmore Water Heaters water heater?

Serial number age decoder for Kenmore Water Heaters tank water heaters: 4 format eras, the decode rule in plain English, transcribed tables, and the official lookup.

Serial number decoder for Kenmore Water Heaters water heater

Serial no.

Type the serial from the data plate, not the model number. Nothing is sent anywhere; the tables are in this page.

Format example: 1210A002243

Kenmore Water Heaters water heater serial numbers in the 2008 to present format encode the year as digits 1-2 (YY) after optional leading S and the week as digits 3-4 (source: building-center.org).
Example: serial 1210A002243 decodes to week 10 of 2012.
Kenmore Water Heaters water heater serial numbers in the before 2010 format encode the year as digits 2-3 (YY) and the month as letter 1 (A=Jan..M=Dec, I skipped) (source: building-center.org).
Example: serial A03307353 decodes to January 2003.
Kenmore Water Heaters water heater serial numbers in the era not stated format encode the year as digits 1-2 (YY; 80 = 1980 per chart) and the week as digits 3-4 (source: building-center.org).
Example: serial 800423049 decodes to week 4 of 1980.

Format eras

before 2010 VERIFIED
A########digits 2-3 (YY)
2008 to present VERIFIED
####A######digits 1-2 (YY) after optional leading S
2008 to present VERIFIED
####A######digits 1-2 (20YY)
era not stated PARTIAL
#########digits 1-2 (YY; 80 = 1980 per chart)

How to read the serial

before 2010 formatVERIFIED

Shape A######## · example A03307353 / J06A059461 · confidence medium

Year: digits 2-3 (YY)
Week or month: month = letter 1 (A=Jan..M=Dec, I skipped)

Month code	Month
A	January
B	February
C	March
D	April
E	May
F	June
G	July
H	August
J	September
K	October
L	November
M	December

Example: serial A03307353 decodes to January 2003.

Trap: A.O. Smith-built units (= AO Smith style 4). Shape identical to Reliance style 1/2 (fiscal table).

Listed under Kenmore water heaters in the source; Kenmore Water Heaters is named in that format's family and the corporate link is an estimate, not a checked fact.

2008 to present formatVERIFIED

Shape ####A###### · example 1210A002243 / S1318 F000046 / 1836111786352 · confidence high

Year: digits 1-2 (YY) after optional leading S
Week or month: week = digits 3-4
Plant: letter after the 4 date digits (unpublished)

Example: serial 1210A002243 decodes to week 10 of 2012.

Trap: Sub-brand applicability (State/American/Reliance/Whirlpool/Kenmore) is ESTIMATE: building-center a-o-smith page covers AO Smith; each sub-brand has its own page to fetch in fan-out. Century: 20YY only for this style.

Listed under A.O. Smith in the source; Kenmore Water Heaters is named in that format's family and the corporate link is an estimate, not a checked fact.

2008 to present formatVERIFIED

Shape ####A###### · example 1210A002243 / S1318 F000046 · confidence high

Year: digits 1-2 (20YY)
Week or month: week = digits 3-4
Plant: letter after date digits

Example: serial 1210A002243 decodes to week 10 of 2012.

Trap: State/Whirlpool-built = A.O. Smith current YYWW style (formats.json rule: ^S?(\d{2})(\d{2})\s?[A-Z]?\d{6,9}$, example 1210A002243)

Listed under Kenmore water heaters in the source; Kenmore Water Heaters is named in that format's family and the corporate link is an estimate, not a checked fact.

era not stated formatPARTIAL

Shape ######### · example 800423049 · confidence low

Year: digits 1-2 (YY; 80 = 1980 per chart)
Week or month: week = digits 3-4

Example: serial 800423049 decodes to week 4 of 1980.

Trap: Labelled 'Rheem style' by building-center, but Rheem's own documented styles are MMYY or year-in-last-digits; 9-digit numeric shape is ambiguous. Low confidence.

Listed under Kenmore water heaters in the source; Kenmore Water Heaters is named in that format's family and the corporate link is an estimate, not a checked fact.

Where the data plate is on a water heater

The rating plate is a large label on the side of the tank near the top or beside the control. The serial is printed on it, often beside the model number and the ANSI standard line.

General guidance, not brand-specific: the owner's manual or the installer can point to the exact spot. See the data plate guide.

For scale only: the InterNACHI Standard Estimated Life Expectancy Chart for Homes lists Water Heater (conventional) at 6 to 12 years of expected service (nachi.org). That chart is a guideline, not a prediction for your unit.

Official lookup: the authority

Open the official A.O. Smith lookup takes serial or reference number; returns warranty status; URL verified live

This site is a reference built from published tables. The manufacturer's own lookup wins whenever the two disagree.

What we could not confirm

Kenmore Water Heaters is treated as sharing A.O. Smith's format because the source lists it in that family; the corporate relationship itself is an estimate.
Kenmore Water Heaters is treated as sharing Kenmore water heaters's format because the source lists it in that family; the corporate relationship itself is an estimate.
The era not stated format is only partially confirmed (PARTIAL).
No official online lookup URL was verified for Kenmore Water Heaters.
Format depends on who built it: AO Smith letter style, Rheem style, or State/Whirlpool YYWW. No Kenmore warranty lookup; kenmore.com is a retail site.

Sources

https://www.building-center.org/a-o-smith/
https://www.building-center.org/kenmore-water-heater-age/
img: KENMORE-1-WH-Serial-Number.jpg
img: KENMORE-2-WH-Serial-Number.jpg