About this site

How Old Is My Unit decodes the manufacture date encoded in equipment serial numbers. It exists because the answer depends entirely on the brand and the era, and the tables that say how are scattered across manufacturer FAQ pages, warranty portals and home-inspector references.

Sources

Every format rule lists its sources on the page that uses it. The primary inspector reference is building-center.org, whose per-brand pages carry chart images that were read and transcribed by hand; manufacturer pages (warranty lookups, serial FAQs) are cited wherever one exists and are stamped official. Life-expectancy figures on category pages come from the InterNACHI Standard Estimated Life Expectancy Chart for Homes.

Method

Research agents wrote one JSON record per format era (brand, product types, era, regex, example serial, how the year and week or month are encoded, transcribed tables, ambiguity, sources, status). A merge script validates each record: the regex must compile, the published example must match it and decode to a plausible year, and a rule with no source is forced to UNSOURCED. Rules that fail are still shown, marked as not evaluated by the decoder, with the reason. Currently 161 of 218 rules are machine-decodable.

Status stamps: VERIFIED means the rule was read from a fetched source page or chart this research cycle; PARTIAL means a source exists but part of the rule (a table, an era boundary) could not be confirmed; UNSOURCED means no source could be found.

What this site does not do

No advice on repair or replacement, no lifespan predictions for your unit, no warranty determinations. The manufacturer's own lookup is the authority for warranty status and for the manufacture date when the tables here are ambiguous. Nothing you type in the decoder leaves your browser.

Update cadence

Rebuilt when research batches land; the tables are historical and change rarely. Rules generated 2026-09-02.

Contact

Corrections welcome, with a source: contact@howoldismyunit.com.