Use this serial number age checker with the number from the data plate and pick the brand. The manufacture week or month and the year are stamped into most HVAC, water heater and appliance serials; this decoder reads them with tables transcribed from manufacturer and inspector sources.
Serial number decoder
Type the serial from the data plate, not the model number. Nothing is sent anywhere; the tables are in this page.
219 brands are catalogued and 126 have at least one sourced, machine-checked serial format (218 formats in total, 167 verified against a fetched source).
A serial number is brand-specific: the same 10-character shape means week-year at Carrier and plant-year-month at Lennox, so the decoder never guesses a brand from the shape.
When a year code repeats (Bradford White every 20 years, York every 21, Whirlpool's 1990s letters reused from 2020), every candidate year is shown, never a silent pick.
When we verified a manufacturer's official lookup, it is linked on that brand page and is the authority whenever it disagrees with a table here.
Each brand page lists every serial format era we could source, as a timeline, with the rule in plain English, the letter tables transcribed, a worked example, and the traps (a 2-digit year with no century, a letter cycle that repeats). The decoder on the page runs those same rules in your browser; nothing is uploaded.
Where a format is only partly confirmed it is stamped PARTIAL, and where no source could be found it is stamped UNSOURCED. Every page ends with what we could not confirm.