diff --git a/esphome/core/__init__.py b/esphome/core/__init__.py
index 84c9e36002..08753b0f2d 100644
--- a/esphome/core/__init__.py
+++ b/esphome/core/__init__.py
@@ -48,6 +48,9 @@ if TYPE_CHECKING:
 
 _LOGGER = logging.getLogger(__name__)
 
+# Key for tracking controller count in CORE.data for ControllerRegistry StaticVector sizing
+KEY_CONTROLLER_REGISTRY_COUNT = "controller_registry_count"
+
 
 class EsphomeError(Exception):
     """General ESPHome exception occurred."""
@@ -912,8 +915,8 @@ class EsphomeCore:
 
     def register_controller(self) -> None:
         """Track registration of a Controller for ControllerRegistry StaticVector sizing."""
-        controller_count = self.data.setdefault("controller_registry_count", 0)
-        self.data["controller_registry_count"] = controller_count + 1
+        controller_count = self.data.setdefault(KEY_CONTROLLER_REGISTRY_COUNT, 0)
+        self.data[KEY_CONTROLLER_REGISTRY_COUNT] = controller_count + 1
 
     @property
     def cpp_main_section(self):
diff --git a/esphome/core/config.py b/esphome/core/config.py
index 3d98eda8bb..ce94ec11f2 100644
--- a/esphome/core/config.py
+++ b/esphome/core/config.py
@@ -40,7 +40,12 @@ from esphome.const import (
     PlatformFramework,
     __version__ as ESPHOME_VERSION,
 )
-from esphome.core import CORE, CoroPriority, coroutine_with_priority
+from esphome.core import (
+    CORE,
+    KEY_CONTROLLER_REGISTRY_COUNT,
+    CoroPriority,
+    coroutine_with_priority,
+)
 from esphome.helpers import (
     copy_file_if_changed,
     fnv1a_32bit_hash,
@@ -465,7 +470,7 @@ async def _add_platform_defines() -> None:
 @coroutine_with_priority(CoroPriority.FINAL)
 async def _add_controller_registry_define() -> None:
     # Generate StaticVector size for ControllerRegistry
-    controller_count = CORE.data.get("controller_registry_count", 0)
+    controller_count = CORE.data.get(KEY_CONTROLLER_REGISTRY_COUNT, 0)
     if controller_count > 0:
         cg.add_define("USE_CONTROLLER_REGISTRY")
         cg.add_define("CONTROLLER_REGISTRY_MAX", controller_count)