Stiebel Eltron water heaters carry the build date inside the serial number.
No reliable published rule exists for Stiebel Eltron serials. The maker can date the unit from the serial number.
A gas tankless water heater usually lasts 15 to 20 years, and sometimes longer, because there is no tank to rust through. Scale buildup in the heat exchanger is what shortens its life.
How long does a tankless water heater last? · Should I replace my water heater? · DC Dept. of Energy & Environment, U.S. DOE Building America
A.O. Smith · American Water Heater · U.S. Craftmaster · Bradford White · State · Reliance · Kenmore · Whirlpool · Rheem · Ruud · Richmond · GE · Marathon · Rinnai · Navien · Noritz · Takagi · Bosch (tankless water heater) · Lochinvar · GSW / John Wood · Paloma · HTP / Westinghouse / American Standard (water heaters) · Giant · EcoSmart / Eemax
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