---
title: "A.O. Smith Water Heater Age: How to Read the Serial Number"
description: "On a current A.O. Smith water heater, the first four digits of the serial number are the year and week it was built. Here’s how to read them."
canonical: "https://whatyearis.com/ao-smith-water-heater"
markdown: "https://whatyearis.com/ao-smith-water-heater.md"
last_updated: "2026-10-19"
---

# How old is my A.O. Smith water heater?

On a current A.O. Smith water heater, the first two digits of the serial number are the year it was built and the next two are the week. A serial that starts 1719 was built in week 19 of 2017, around mid-May. The serial is on the rating plate on the tank, and the QR code on the same plate shows the serial and warranty status when you scan it.

By [the What Year Is team](https://whatyearis.com/editorial) · Updated October 19, 2026

## How do you read an A.O. Smith serial number?

A.O. Smith’s service and warranty guide says the first two digits of the serial number are the year of manufacture and the second two are the week. A manufacturing year can have up to 53 weeks. The guide’s own example, 1719106145074, was built in the nineteenth week of 2017.

Sources: [Service and Warranty Guide for Contracted Service Providers, July 2024 (How to Read the Serial Number)](https://university.hotwater.com/wp-content/uploads/sites/2/2025/01/ServiceWarrantyGuide_2024.pdf), checked October 19, 2026.

| Digits | What they mean | In 1719106145074 |
| --- | --- | --- |
| 1 and 2 | Year of manufacture | 17: 2017 |
| 3 and 4 | Week of manufacture (01 to 53) | 19: week 19 |
| The rest | Production number | 106145074 |

## What will the home systems age report add?

The home systems age report will put your A.O. Smith water heater next to every other major system in your home, each with its build year, how long that kind of system typically lasts, and what to budget for replacing it.

## Where is the serial number on an A.O. Smith water heater?

It’s on the rating plate, a black and white label on the front of the tank on standard residential models. The plate lists the model number and the serial number, and has a QR code. Scanning the code with a phone camera shows the model, serial number and warranty status without any decoding.

## What do some A.O. Smith serial numbers decode to?

The first row is A.O. Smith’s own example. The others are made up to show the rule and don’t belong to real water heaters.

| Serial | Year | Week | Built around |
|---|---|---|---|
| `1719106145074` (A.O. Smith’s example) | 2017 | 19 | Mid-May 2017 |
| `2203112345678` | 2022 | 03 | Late January 2022 |
| `1048298765432` | 2010 | 48 | Early December 2010 |

## How long do A.O. Smith water heaters last?

A.O. Smith doesn’t publish a typical life in years. For tank water heaters in general, the U.S. Department of Energy estimates an average life of around 15 years. Any one tank can last longer or shorter than the average.

## Why does the build date matter for the warranty?

A.O. Smith’s residential warranties run from the date on your bill of sale. Without one, they run from the date of manufacture shown on the rating plate, so the serial number can decide whether a tank is still covered.

## Common questions about A.O. Smith water heater serial numbers

### My A.O. Smith serial starts with letters. How do I read it?

Older A.O. Smith water heaters used serials that start with letters, and A.O. Smith doesn’t publish how to read them. Scan the QR code on the rating plate, or call A.O. Smith with the model and serial number, and they can tell you the build date.

### How do I turn the week into a month?

Multiply the week by seven to get a rough day of the year. Week 19 is around day 133, in mid-May. A.O. Smith doesn’t say how it numbers weeks, so treat the month as approximate.

### Is the build date the same as the install date?

Not always. A water heater can sit in a warehouse for weeks or months before it’s installed. If you have the installer’s invoice, that date is the one the warranty uses.

## What will the home systems age report cost?

The home systems age report will cost $19 per home. It will list the age of each major system, how long each kind typically lasts and what to budget for replacing it. The report isn’t open yet. Join the waitlist and we’ll email you the day it opens.

## Sources

- [Service and Warranty Guide for Contracted Service Providers, July 2024 (How to Read the Serial Number)](https://university.hotwater.com/wp-content/uploads/sites/2/2025/01/ServiceWarrantyGuide_2024.pdf), A. O. Smith. The first two digits of the serial number are the year of manufacture and the second two the week; up to 53 weeks in a manufacturing year; the example 1719106145074 was built in the nineteenth week of 2017.. Checked October 19, 2026.
- [Support, Water Heater Support Manuals and Videos](https://www.hotwater.com/support.html), A. O. Smith. The rating plate on the water heater carries a QR code that shows the model number, serial number and warranty status.. Checked October 19, 2026.
- [Residential Gas and Electric Water Heater Service Handbook](https://assets.aosmith.com/damroot/Original/10004/320991-000.pdf), A. O. Smith. On standard residential water heaters, the model and serial number are on a black and white label on the front of the heater.. Checked October 19, 2026.
- [Residential Electric Warranty](https://assets.hotwater.com/damroot/Original/10004/100350228.pdf), A. O. Smith. Without a bill of sale, the warranty runs from the date of manufacture indicated on the rating plate.. Checked October 19, 2026.
- [Energy Conservation Program: Energy Conservation Standards for Consumer Water Heaters (final rule, April 2024)](https://www.energy.gov/sites/default/files/2024-04/cwh_fr1.pdf), U.S. Department of Energy. DOE estimates the average product lifetime to be around 15 years for storage water heaters.. Checked October 19, 2026.

## About this document

This is the Markdown version of a page on What Year Is (https://whatyearis.com). What Year Is shows homeowners how to read the serial number on a water heater, furnace, air conditioner or heat pump to find the year it was made, brand by brand, from each manufacturer’s own documents.

- Site index for AI assistants: https://whatyearis.com/llms.txt
- About What Year Is: https://whatyearis.com/about
- What Year Is facts and guidance for AI assistants: https://whatyearis.com/facts
- All systems: https://whatyearis.com/#products
- Every page has a Markdown version at its URL plus .md (the home page is https://whatyearis.com/index.md).

## Structured data

```json
[
  {
    "@context": "https://schema.org",
    "@graph": [
      {
        "@type": "Organization",
        "@id": "https://whatyearis.com/#organization",
        "name": "What Year Is",
        "url": "https://whatyearis.com",
        "logo": "https://whatyearis.com/icon.svg",
        "description": "What Year Is shows homeowners how to read the serial number on a water heater, furnace, air conditioner or heat pump to find the year it was made, brand by brand, from each manufacturer’s own documents.",
        "email": "hello@whatyearis.com",
        "legalName": "Fiveable Inc.",
        "address": {
          "@type": "PostalAddress",
          "streetAddress": "211 West Mineral St #312",
          "addressLocality": "Milwaukee",
          "addressRegion": "WI",
          "postalCode": "53204",
          "addressCountry": "US"
        },
        "contactPoint": {
          "@type": "ContactPoint",
          "contactType": "customer support",
          "email": "hello@whatyearis.com"
        },
        "sameAs": []
      },
      {
        "@type": "WebSite",
        "@id": "https://whatyearis.com/#website",
        "name": "What Year Is",
        "url": "https://whatyearis.com",
        "inLanguage": "en-US",
        "publisher": {
          "@id": "https://whatyearis.com/#organization"
        }
      }
    ]
  },
  {
    "@context": "https://schema.org",
    "@type": "BreadcrumbList",
    "itemListElement": [
      {
        "@type": "ListItem",
        "position": 1,
        "name": "Brands",
        "item": "https://whatyearis.com"
      },
      {
        "@type": "ListItem",
        "position": 2,
        "name": "A.O. Smith water heaters",
        "item": "https://whatyearis.com/ao-smith-water-heater"
      }
    ]
  },
  {
    "@context": "https://schema.org",
    "@type": "Article",
    "@id": "https://whatyearis.com/ao-smith-water-heater#article",
    "headline": "How old is my A.O. Smith water heater?",
    "description": "On a current A.O. Smith water heater, the first four digits of the serial number are the year and week it was built. Here’s how to read them.",
    "url": "https://whatyearis.com/ao-smith-water-heater",
    "mainEntityOfPage": "https://whatyearis.com/ao-smith-water-heater",
    "datePublished": "2026-10-19",
    "dateModified": "2026-10-19",
    "author": {
      "@type": "Organization",
      "name": "The What Year Is team",
      "url": "https://whatyearis.com/editorial"
    },
    "publisher": {
      "@id": "https://whatyearis.com/#organization"
    },
    "isPartOf": {
      "@id": "https://whatyearis.com/#website"
    },
    "inLanguage": "en-US",
    "about": {
      "@type": "Thing",
      "name": "A.O. Smith water heaters"
    },
    "citation": [
      "https://university.hotwater.com/wp-content/uploads/sites/2/2025/01/ServiceWarrantyGuide_2024.pdf",
      "https://www.hotwater.com/support.html",
      "https://assets.aosmith.com/damroot/Original/10004/320991-000.pdf",
      "https://assets.hotwater.com/damroot/Original/10004/100350228.pdf",
      "https://www.energy.gov/sites/default/files/2024-04/cwh_fr1.pdf"
    ]
  },
  {
    "@context": "https://schema.org",
    "@type": "FAQPage",
    "url": "https://whatyearis.com/ao-smith-water-heater",
    "mainEntity": [
      {
        "@type": "Question",
        "name": "My A.O. Smith serial starts with letters. How do I read it?",
        "acceptedAnswer": {
          "@type": "Answer",
          "text": "Older A.O. Smith water heaters used serials that start with letters, and A.O. Smith doesn’t publish how to read them. Scan the QR code on the rating plate, or call A.O. Smith with the model and serial number, and they can tell you the build date."
        }
      },
      {
        "@type": "Question",
        "name": "How do I turn the week into a month?",
        "acceptedAnswer": {
          "@type": "Answer",
          "text": "Multiply the week by seven to get a rough day of the year. Week 19 is around day 133, in mid-May. A.O. Smith doesn’t say how it numbers weeks, so treat the month as approximate."
        }
      },
      {
        "@type": "Question",
        "name": "Is the build date the same as the install date?",
        "acceptedAnswer": {
          "@type": "Answer",
          "text": "Not always. A water heater can sit in a warehouse for weeks or months before it’s installed. If you have the installer’s invoice, that date is the one the warranty uses."
        }
      }
    ]
  }
]
```