diff --git a/esphome/core/__init__.py b/esphome/core/__init__.py
index 721cd5787d..5ce968f20d 100644
--- a/esphome/core/__init__.py
+++ b/esphome/core/__init__.py
@@ -608,6 +608,8 @@ class EsphomeCore:
         self.current_component: str | None = None
         # Address cache for DNS and mDNS lookups from command line arguments
         self.address_cache: AddressCache | None = None
+        # Cached config hash (computed lazily)
+        self._config_hash: int | None = None
 
     def reset(self):
         from esphome.pins import PIN_SCHEMA_REGISTRY
@@ -636,6 +638,7 @@ class EsphomeCore:
         self.unique_ids = {}
         self.current_component = None
         self.address_cache = None
+        self._config_hash = None
         PIN_SCHEMA_REGISTRY.reset()
 
     @contextmanager
@@ -685,6 +688,20 @@ class EsphomeCore:
 
         return None
 
+    @property
+    def config_hash(self) -> int:
+        """Get the FNV-1a 32-bit hash of the config.
+
+        The hash is computed lazily and cached for performance.
+        """
+        if self._config_hash is None:
+            from esphome import yaml_util
+            from esphome.helpers import fnv1a_32bit_hash
+
+            config_str = yaml_util.dump(self.config, show_secrets=True)
+            self._config_hash = fnv1a_32bit_hash(config_str)
+        return self._config_hash
+
     @property
     def config_dir(self) -> Path:
         if self.config_path.is_dir():
diff --git a/esphome/writer.py b/esphome/writer.py
index 11e10d2fd4..629329cbb1 100644
--- a/esphome/writer.py
+++ b/esphome/writer.py
@@ -21,7 +21,6 @@ from esphome.const import (
 from esphome.core import CORE, EsphomeError
 from esphome.helpers import (
     copy_file_if_changed,
-    fnv1a_32bit_hash,
     get_str_env,
     is_ha_addon,
     read_file,
@@ -300,11 +299,7 @@ def get_build_info() -> tuple[int, int, str]:
     Returns:
         Tuple of (config_hash, build_time, build_time_str)
     """
-    from esphome import yaml_util
-
-    # Use the same clean YAML representation as 'esphome config' command
-    config_str = yaml_util.dump(CORE.config, show_secrets=True)
-    config_hash = fnv1a_32bit_hash(config_str)
+    config_hash = CORE.config_hash
 
     # Check if config_hash and version are unchanged - keep existing build_time
     build_info_path = CORE.relative_build_path("build_info.json")