How old is my State water heater?

Q: How old is my State water heater?

State is the one brand in this family where the published references disagree. InspectApedia's State page says State Industries encode the age in the first three positions as a month letter plus a two-digit year, so a serial starting A00 is January 2000, with a four-digit variant where 0910 is September 2010. Fast Water Heater instead groups State with A.O. Smith and reads the first four digits as year then week. The test is simple: if your serial starts with a letter, use the month-letter rule, and if it starts with four digits, you have to settle which of the two applies.

Start here: does your serial begin with a letter?

That single question decides which rule applies, and it resolves most plates without any further thought.

Serial begins with	Use	Example
a letter	month letter, then two-digit year	A00114092 is January 2000
four digits	see the conflict below	0910123456 or 1220345678

The rule on InspectApedia's State page

InspectApedia states it directly: "State water heaters, produced by State Industries, encode the age in the first three positions of the State water heater serial number as MYY nnnn. Where M is a one-letter month code, encoded corresponding to A = January through M = December and the second two digits are the numeric year."

And a four-position variant: "On some State water heaters, age is encoded in the first four positions of the State or Apollo Comfort Products Water Heater serial number as MMYY nnnnn such as 0910123456 where the heater was made September 2010."

A worked example from their own page, where a reader posted serial A00114092 and the moderator confirmed the reading: January 2000. A is the first month letter, 00 is the year.

The month letters are the same set used across this family, twelve letters with I left out:

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

The conflict, stated plainly

Our two references do not agree, and we are not going to pretend otherwise.

Source	Reading of the first four digits	0910 becomes
InspectApedia, State page	month then year (MMYY)	September 2010
Fast Water Heater	year then week (YYWW)	week 10 of 2009

Fast Water Heater lists "American Water Heater, A.O. Smith, State, Reliance & Whirlpool" together and says of all of them that "the first two digits are the year, the next two are the week of that year."

InspectApedia adds a third note that shows the disagreement is older than this page: "Note that I've seen some guides claiming the opposite encoding, that is YYMMnnnnn."

Our position, marked as ours. We cannot resolve this from the published sources, so we will not invent a winner. What we can give you is a test that works in practice:

If the first pair is above 12, it cannot be a month. Read it as a year under the Fast Water Heater rule, or as a week under the older-guide reading. A serial starting 1520 is not month 15.
If the second pair is above 12 but the first is not, the second pair is far more likely a week or a year than a month, which points at the InspectApedia MMYY reading.
If both pairs are 12 or below, both rules give a plausible date and you cannot tell from the number alone. Then use the age bracket instead: compare the two candidate years against the condition of the tank, the style of the label, and any installation paperwork.
When it matters for a warranty claim, do not rely on either rule. State publishes product registration and support, so have the serial checked against the manufacturer's record. What those warranties actually cover, and whether the longer one pays, is on the warranty page.

This is the honest answer. A decoder that hands you one confident date here is hiding a disagreement that exists in the literature.

Which badges State Industries built

This is the longest brand list in the family, and it is the reason a plate that says something else entirely may still decode by the rules above. InspectApedia names: Ace, Ambassador, Apollo Comfort Products, Arco, Barnett, Century, Crosley, Energy Stretcher, Freedom, Hardware House, Intertherm, Kenmore, Master Plumber, Master Plumber True5, Mission, National line and Nationaline, Nordyne, Patriot, Penfield, President, Regency, Reliance, Sears, State Industries, State, The Plumbery, Thermo-king and Top Line.

Note that both Kenmore and Sears appear there. That is consistent with the correction we made to our age decoder on 8 October 2026: Kenmore belongs on this side of the industry, not with Rheem.

Where State sits in the industry

InspectApedia's A.O. Smith page records that A.O. Smith "by 2006 had purchased both Canadian GSW Incorporated and the American Water Heater Company", and lists State's contact address as 500 Tennessee Waltz Pkwy, the same Ashland City, Tennessee address it gives for A.O. Smith Water Heaters.

So State is today an A.O. Smith brand, which is why Fast Water Heater files it under the family rule. The serial formats on older State tanks predate that, which is the most likely reason the two references part company. That explanation is ours and we cannot prove it, but it fits both sets of facts better than either source being simply wrong.

What the age tells you

Once you have a year, or a pair of candidate years, the repair or replace page turns it into a decision and the expected life page gives the bands by type. For a brand built in the same plants, see A.O. Smith and Whirlpool.

Sources

Price figures are national US ranges from the sources above as of the date shown. Your local price depends on labor rates, permits and site conditions. Read how we get our numbers.