diff --git a/src/calng/base_calcat.py b/src/calng/base_calcat.py
index 40965e9cdec7744bee23270bb7baa6b62fc1218d..09fce8d3a78f3c971988b9afbea7bfdb6d23915b 100644
--- a/src/calng/base_calcat.py
+++ b/src/calng/base_calcat.py
@@ -23,6 +23,7 @@ from karabo.bound import (
     STRING_ELEMENT,
     UINT32_ELEMENT,
     VECTOR_UINT32_ELEMENT,
+    Unit,
 )
 
 from . import utils
@@ -185,6 +186,15 @@ def add_status_schema_from_enum(schema, enum_class):
             .reconfigurable()
             .commit(),
 
+            DOUBLE_ELEMENT(schema)
+            .key(f"{constant_node}.constantLoadingTime")
+            .displayedName("FS load time")
+            .unit(Unit.SECOND)
+            .description("How long it took loading this constant from the file system")
+            .readOnly()
+            .initialValue(0)
+            .commit(),
+
             SLOT_ELEMENT(schema)
             .key(f"{constant_node}.overrideConstantFromFile")
             .displayedName("Override from file")
@@ -567,9 +577,11 @@ class BaseCalcatFriend:
         self._set_status(constant, "dataFilePath", str(file_path))
         self._set_status(constant, "dataSetName", resp["data"]["data_set_name"])
 
-        constant_data = _read_dataset_externally(
-            file_path, resp["data"]["data_set_name"]
-        )
+        with utils.Stopwatch() as stopwatch:
+            constant_data = _read_dataset_externally(
+                file_path, resp["data"]["data_set_name"]
+            )
+        self._set_status(constant, "constantLoadingTime", stopwatch.elapsed)
 
         with self.cached_constants_lock:
             self.cached_constants[constant] = constant_data
@@ -594,9 +606,13 @@ class BaseCalcatFriend:
         )
         self._set_status(constant, "dataFilePath", str(file_path))
         self._set_status(constant, "dataSetName", resp["data"]["data_set_name"])
-        constant_data = _read_dataset_externally(
-            file_path, resp["data"]["data_set_name"]
-        )
+
+        with utils.Stopwatch() as stopwatch:
+            constant_data = _read_dataset_externally(
+                file_path, resp["data"]["data_set_name"]
+            )
+        self._set_status(constant, "constantLoadingTime", stopwatch.elapsed)
+
         with self.cached_constants_lock:
             self.cached_constants[constant] = constant_data
         self._set_status(constant, "beginValidityAt", resp["data"]["begin_at"])
@@ -608,10 +624,13 @@ class BaseCalcatFriend:
         return constant_data
 
     def get_constant_from_file(self, constant):
-        constant_data = _read_dataset_externally(
-            self.device.get(f"foundConstants.{constant.name}.dataFilePath"),
-            self.device.get(f"foundConstants.{constant.name}.dataSetName"),
-        )
+        with utils.Stopwatch() as stopwatch:
+            constant_data = _read_dataset_externally(
+                self.device.get(f"foundConstants.{constant.name}.dataFilePath"),
+                self.device.get(f"foundConstants.{constant.name}.dataSetName"),
+            )
+        self._set_status(constant, "constantLoadingTime", stopwatch.elapsed)
+
         with self.cached_constants_lock:
             self.cached_constants[constant] = constant_data
         self._set_status(constant, "beginValidityAt", "manual override")