Navien tankless water heater code E615
Input and memory fault. Code E615 means the same thing on all 2 Navien series documented here — but the fix, and what it costs, is still worth reading for your exact unit.
What code E615 means on each Navien series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| NPE-2 | Input and memory fault | Call a pro | $200–$1,100 |
| NPE-A / NPE-S | Input and memory fault | Call a pro | $200–$1,100 |
Each row opens the full page for that generation. We hold manuals for NPE-2 and NPE-A / NPE-S, and each one gets its own reading of code E615 — what Navien documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 2 series in four columns, which is enough to route you and not enough to explain anything. This is the Navien wording behind each row, one entry per manual, so you can see where the 2 readings of code E615 agree and where they part company.
NPE-2 — Input and memory fault
The board is reporting a fault between what it is being told and what it has stored. Navien groups it with the other board-level faults and gives no owner-level step: contact technical support.
NPE-A / NPE-S — Input and memory fault
The board's stored configuration or its inputs are not reading back correctly. Navien's instruction is to contact technical support; there is no owner-side remedy.
Does it matter which Navien you have?
NPE-2 and NPE-A / NPE-S all route code E615 the same way: a professional, at $200–$1,100. That makes it one of the Navien numbers you can act on before working out which unit you own.
Which Navien do you have?
On the 2 series that report code E615, the model number on the rating label starts NPE — match yours against the 13 listed below. You can also use the full model-number decoder.
Where this comes from
Source: Navien NPE-2 User's Information Manual (p. 17), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Source: Navien NPE Operation Manual (NPE-A / NPE-S) (p. 16), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Parts, guides and symptoms behind code E615
Code E615 on these 2 Navien series points at 1 part and 1 symptom, each named by the manufacturer's own procedure for this code.