The Age of an A.O. Smith Water Heater Is Found in Its Serial Number

Determine your water heater's age by decoding the serial number on its rating plate. The first four characters (letters/digits) typically represent the manufacture date, with the first two indicating the year and the next two the month. Locate the plate near the top of the unit for accurate results.

Where to Find the Serial Number

• Rating plate: A white or silver sticker near the top of the tank (front or side).
• Format: Begins with letters/numbers (e.g., G123456789 or 1023A12345).
• Alternative locations: Under the insulation blanket (if covered) or on the back for some models.

How to Decode the Serial Number

The first 4 characters are key. A.O. Smith uses two common formats:

1. Letter-Year Format (Older Models):
   • First letter = year (e.g., G = 2016, H = 2017). Use the letter-to-year chart below.
   • Next 2 digits = month (e.g., 05 = May).
   • Example: G05 = May 2016.
2. Number-Year Format (Newer Models):
   • First 2 digits = year (e.g., 23 = 2023).
   • Next 2 digits = month (e.g., 11 = November).
   • Example: 2311 = November 2023.

Letter-to-Year Conversion Chart

Troubleshooting Unclear Serial Numbers

• Worn/sticker damage: Check for partial numbers or contact the manufacturer with the full serial.
• Non-standard formats: Some models use YYMM (e.g., 9912 = December 1999).
• Missing plate: Look for installation records or receipts with purchase dates.

Why Age Matters

• Lifespan: Most water heaters last 8-12 years. Replace if near/exceeding this range.
• Warranty: A.O. Smith warranties typically cover 6-12 years (check your model).
• Efficiency: Older units (>10 years) lose efficiency, increasing energy costs.

Comparison: Signs Your Water Heater Needs Replacement