Read the plate. Check the evidence.
Find supported Energy Master water-heater date codes, older brand-label context and the separate model number needed for manuals. Confirm the manufacturer and serial system before decoding.
Browse Energy Master manuals and guides →Check a documented system
Water heaters with confirmed manufacturer and numbering family; unrelated devices using the same name are outside these date-code rules.
Choose the equipment family
Match the product, manufacturer and documented serial layout before interpreting a date. The model is a separate label field; a date code alone does not identify capacity, installation date or warranty entitlement.
For Energy Master water-heater labels: for a confirmed matching Rheem-built water heater, older serials can encode month/year before a plant-line letter. Documented later systems use plant, week and year. Plant changes occurred individually. These are water-heater rules; an HVAC serial or a newer product from another builder needs its own documentation.
Scope matters
Research reviewed October 16, 2026. This independent tool applies published rules and retains unresolved years and model candidates.
Water heaters only after confirmation of this manufacturer, product family, date-code layout and documented era.
Old water-heater suffix MMYY plant-line + five sequence digits. Manufacturer example 1209 D 01234 = December 2009. Optional brand prefix is not part of the 10-character date format. Modern plants changed individually from 2012; do not assume old-style serial ceased at every plant that year. The supplied historical inspection chart lists additional names, but that relationship does not prove the manufacturer of every product bearing the same brand. This option requires independent confirmation from the unit label or model-specific documentation.
Confirm that this is a water heater and that its rating plate or model-specific manufacturer documentation uses this exact numbering family. A historical brand list or a matching serial shape alone is insufficient.
Water heaters only after confirmation of this manufacturer, product family, date-code layout and documented era.
TSB 1207 starts Mexicali April 2, 2012 and Nuevo Laredo June 4, 2012; plants migrate individually. PWWYY 00001 plus optional conversion-letter suffix. Plant identifies a city/country/organization only, never an exact street. Brand/fuel prefix can precede P. The supplied historical inspection chart lists additional names, but that relationship does not prove the manufacturer of every product bearing the same brand. This option requires independent confirmation from the unit label or model-specific documentation.
Confirm that this is a water heater and that its rating plate or model-specific manufacturer documentation uses this exact numbering family. A historical brand list or a matching serial shape alone is insufficient.
Only the supplied 2010 Rheem-family water-heater chart; not generic GE/Intertherm HVAC or other products.
Secondary evidence illustrates 0794******as July 1994. Existing manufacturer-corroborated MMYY/letter/sequence water-heater rules remain unchanged. Current Rheem official pages support MMYY meanings on a different 10-character example 1209 D 01234; that does not independently prove every numeric-only historic suffix.
Select only after confirming the water heater or boiler family and numbering system described here. Brand ownership alone does not establish this system.
Reading your result
Some systems reuse letters or only encode the last one or two year digits. Every supported interpretation is retained. A decade supplied from reliable records can narrow the reading; the tool does not automatically pick the newest year.
Usually the model is a separate plate field. Where published serial ranges actually identify a model, the result shows model candidates and links to their manuals. Overlapping ranges remain ambiguous.
After a lookup, the address includes the serial in a fragment beginning with #serial=. Use “Copy share link” to share the serial and selected context. Opening the link runs the same lookup. The fragment is not a query-string result page.