diff --git a/homeassistant/components/tankerkoenig/diagnostics.py b/homeassistant/components/tankerkoenig/diagnostics.py
index 811ec07ef19..d5fd7c8cada 100644
--- a/homeassistant/components/tankerkoenig/diagnostics.py
+++ b/homeassistant/components/tankerkoenig/diagnostics.py
@@ -1,6 +1,7 @@
 """Diagnostics support for Tankerkoenig."""
 from __future__ import annotations
 
+from dataclasses import asdict
 from typing import Any
 
 from homeassistant.components.diagnostics import async_redact_data
@@ -27,6 +28,9 @@ async def async_get_config_entry_diagnostics(
 
     diag_data = {
         "entry": async_redact_data(entry.as_dict(), TO_REDACT),
-        "data": coordinator.data,
+        "data": {
+            station_id: asdict(price_info)
+            for station_id, price_info in coordinator.data.items()
+        },
     }
     return diag_data
diff --git a/tests/components/tankerkoenig/snapshots/test_diagnostics.ambr b/tests/components/tankerkoenig/snapshots/test_diagnostics.ambr
index a27a210c46e..f52cb3a88a5 100644
--- a/tests/components/tankerkoenig/snapshots/test_diagnostics.ambr
+++ b/tests/components/tankerkoenig/snapshots/test_diagnostics.ambr
@@ -3,8 +3,10 @@
   dict({
     'data': dict({
       '3bcd61da-xxxx-xxxx-xxxx-19d5523a7ae8': dict({
-        '__type': "<class 'aiotankerkoenig.models.PriceInfo'>",
-        'repr': "PriceInfo(status=<Status.OPEN: 'open'>, e5=1.719, e10=1.659, diesel=1.659)",
+        'diesel': 1.659,
+        'e10': 1.659,
+        'e5': 1.719,
+        'status': 'open',
       }),
     }),
     'entry': dict({