diff --git a/homeassistant/components/chromecast.py b/homeassistant/components/chromecast.py
index 3bfc79d58e8..7ce36384994 100644
--- a/homeassistant/components/chromecast.py
+++ b/homeassistant/components/chromecast.py
@@ -17,7 +17,6 @@ SERVICE_YOUTUBE_VIDEO = 'play_youtube_video'
 ENTITY_ID_FORMAT = DOMAIN + '.{}'
 STATE_NO_APP = 'no_app'
 
-ATTR_FRIENDLY_NAME = 'friendly_name'
 ATTR_HOST = 'host'
 ATTR_STATE = 'state'
 ATTR_OPTIONS = 'options'
@@ -100,13 +99,14 @@ def setup(bus, statemachine):
 
     casts = {}
 
-    eid_form = ENTITY_ID_FORMAT.format
-
     for host in hosts:
         try:
             cast = pychromecast.PyChromecast(host)
 
-            entity_id = eid_form(util.slugify(cast.device.friendly_name))
+            entity_id = util.ensure_unique_string(
+                ENTITY_ID_FORMAT.format(
+                    util.slugify(cast.device.friendly_name)),
+                casts.keys())
 
             casts[entity_id] = cast
 
@@ -124,7 +124,8 @@ def setup(bus, statemachine):
         status = chromecast.app
 
         state_attr = {ATTR_HOST: chromecast.host,
-                      ATTR_FRIENDLY_NAME: chromecast.device.friendly_name}
+                      components.ATTR_FRIENDLY_NAME:
+                      chromecast.device.friendly_name}
 
         if status and status.app_id != pychromecast.APP_ID['HOME']:
             state = status.app_id
diff --git a/homeassistant/components/light.py b/homeassistant/components/light.py
index e1fcb9d9585..5df19e7dbc5 100644
--- a/homeassistant/components/light.py
+++ b/homeassistant/components/light.py
@@ -14,7 +14,7 @@ import homeassistant as ha
 import homeassistant.util as util
 from homeassistant.components import (group, STATE_ON, STATE_OFF,
                                       SERVICE_TURN_ON, SERVICE_TURN_OFF,
-                                      ATTR_ENTITY_ID)
+                                      ATTR_ENTITY_ID, ATTR_FRIENDLY_NAME)
 
 
 DOMAIN = "light"
@@ -93,30 +93,24 @@ def setup(bus, statemachine, light_control):
 
     def _update_light_state(light_id, light_state):
         """ Update statemachine based on the LightState passed in. """
+        name = light_control.get_name(light_id) or "Unknown Light"
+
         try:
             entity_id = light_to_ent[light_id]
         except KeyError:
             # We have not seen this light before, set it up
 
-            # Get name and create entity id
-            name = light_control.get_name(light_id) or "Unknown Light"
-
+            # Create entity id
             logger.info(u"Found new light {}".format(name))
 
-            entity_id = ENTITY_ID_FORMAT.format(util.slugify(name))
-
-            # Ensure unique entity id
-            tries = 1
-            while entity_id in ent_to_light:
-                tries += 1
-
-                entity_id = ENTITY_ID_FORMAT.format(
-                    util.slugify("{} {}".format(name, tries)))
+            entity_id = util.ensure_unique_string(
+                ENTITY_ID_FORMAT.format(util.slugify(name)),
+                ent_to_light.keys())
 
             ent_to_light[entity_id] = light_id
             light_to_ent[light_id] = entity_id
 
-        state_attr = {}
+        state_attr = {ATTR_FRIENDLY_NAME: name}
 
         if light_state.on:
             state = STATE_ON
diff --git a/homeassistant/components/wemo.py b/homeassistant/components/wemo.py
index 3517943274d..c90f205ab01 100644
--- a/homeassistant/components/wemo.py
+++ b/homeassistant/components/wemo.py
@@ -74,7 +74,9 @@ def setup(bus, statemachine):
 
         except KeyError:
             # New device, set it up
-            entity_id = ENTITY_ID_FORMAT.format(util.slugify(device.name))
+            entity_id = util.ensure_unique_string(
+                ENTITY_ID_FORMAT.format(util.slugify(device.name)),
+                ent_to_dev.keys())
 
             sno_to_ent[device.serialnumber] = entity_id
             ent_to_dev[entity_id] = device
diff --git a/homeassistant/util.py b/homeassistant/util.py
index 0d1007ac10c..c29284541e2 100644
--- a/homeassistant/util.py
+++ b/homeassistant/util.py
@@ -119,6 +119,20 @@ def convert(value, to_type, default=None):
         return default
 
 
+def ensure_unique_string(preferred_string, current_strings):
+    """ Returns a string that is not present in current_strings.
+        If preferred string exists will append _2, _3, .. """
+    string = preferred_string
+
+    tries = 1
+
+    while preferred_string in current_strings:
+        tries += 1
+        string = "{}_{}".format(preferred_string, tries)
+
+    return string
+
+
 # Reason why I decided to roll my own ThreadPool instead of using
 # multiprocessing.dummy.pool or even better, use multiprocessing.pool and
 # not be hurt by the GIL in the cpython interpreter: