diff --git a/homeassistant/components/sensor/moon.py b/homeassistant/components/sensor/moon.py
index 0c57c98c0af..d909eb3c0f2 100644
--- a/homeassistant/components/sensor/moon.py
+++ b/homeassistant/components/sensor/moon.py
@@ -50,20 +50,20 @@ class MoonSensor(Entity):
     def state(self):
         """Return the state of the device."""
         if self._state == 0:
-            return 'New moon'
+            return 'new_moon'
         elif self._state < 7:
-            return 'Waxing crescent'
+            return 'waxing_crescent'
         elif self._state == 7:
-            return 'First quarter'
+            return 'first_quarter'
         elif self._state < 14:
-            return 'Waxing gibbous'
+            return 'waxing_gibbous'
         elif self._state == 14:
-            return 'Full moon'
+            return 'full_moon'
         elif self._state < 21:
-            return 'Waning gibbous'
+            return 'waning_gibbous'
         elif self._state == 21:
-            return 'Last quarter'
-        return 'Waning crescent'
+            return 'last_quarter'
+        return 'waning_crescent'
 
     @property
     def icon(self):
diff --git a/homeassistant/components/sensor/strings.moon.json b/homeassistant/components/sensor/strings.moon.json
new file mode 100644
index 00000000000..97d96623d88
--- /dev/null
+++ b/homeassistant/components/sensor/strings.moon.json
@@ -0,0 +1,12 @@
+{
+  "state": {
+    "new_moon": "New moon",
+    "waxing_crescent": "Waxing crescent",
+    "first_quarter": "First quarter",
+    "waxing_gibbous": "Waxing gibbous",
+    "full_moon": "Full moon",
+    "waning_gibbous": "Waning gibbous",
+    "last_quarter": "Last quarter",
+    "waning_crescent": "Waning crescent"
+  }
+}
diff --git a/tests/components/sensor/test_moon.py b/tests/components/sensor/test_moon.py
index 334dd9a0bec..9086df6e79b 100644
--- a/tests/components/sensor/test_moon.py
+++ b/tests/components/sensor/test_moon.py
@@ -37,7 +37,7 @@ class TestMoonSensor(unittest.TestCase):
         assert setup_component(self.hass, 'sensor', config)
 
         state = self.hass.states.get('sensor.moon_day1')
-        self.assertEqual(state.state, 'Waxing crescent')
+        self.assertEqual(state.state, 'waxing_crescent')
 
     @patch('homeassistant.components.sensor.moon.dt_util.utcnow',
            return_value=DAY2)
@@ -53,4 +53,4 @@ class TestMoonSensor(unittest.TestCase):
         assert setup_component(self.hass, 'sensor', config)
 
         state = self.hass.states.get('sensor.moon_day2')
-        self.assertEqual(state.state, 'Waning gibbous')
+        self.assertEqual(state.state, 'waning_gibbous')