How old is my HTP unit?

HTP is part of HTP / Ariston. 3 serial formats sourced across boiler, water heater.

Serial number decoder for HTP

Serial no.

Type the serial from the data plate, not the model number. Nothing is sent anywhere; the tables are in this page.

Format example: I21M28666

HTP boiler serial numbers in the 1994 to 2011 format encode the year as letter 2 (4th char) (table below) and the month as letter 1 (A=Jan..L=Dec, I=Sep, 12 consecutive letters); day of month as digits 2-3 (source: htproducts.com).
Example: serial I21M28666 decodes to September 2006.
HTP boiler serial numbers in the 2011 to 2021 format encode the year as digits 5-6 (20YY) after dropping a 2-digit prefix when the serial is 16 digits and the month as digits 1-2, day as digits 3-4; the letter = production line (source: htproducts.com).
Example: serial 112116E2054485 decodes to November 2016.
HTP boiler serial numbers in the 2021 to present format encode the year as digits 10-11 (20YY) and the day of year = digits 12-14 (045 = Feb 14) (source: htproducts.com).
Example: serial 3251200U4220450000188 decodes to day 45 of 2022.
HTP's official lookup at htproducts.com returns warranty / registration lookup.

Decoder pages by product

Official lookup: the authority

Open the official HTP lookup takes serial number; returns warranty / registration lookup; URL verified live

This site is a reference built from published tables. The manufacturer's own lookup wins whenever the two disagree.

Official PDF 'UnderstandSerialNumbers-2-2024.pdf' fully documents 3 HTP eras + 2 Ariston formats. Warranty Wizard (htp.my.site.com) takes a serial number; 'Find Serial Numbers' PDF gives label locations.