diff --git a/homeassistant/components/geniushub/sensor.py b/homeassistant/components/geniushub/sensor.py
index ef148b48143..a52bd2d692f 100644
--- a/homeassistant/components/geniushub/sensor.py
+++ b/homeassistant/components/geniushub/sensor.py
@@ -1,11 +1,12 @@
 """Support for Genius Hub sensor devices."""
-from datetime import datetime
+from datetime import timedelta
 import logging
 
 from homeassistant.const import DEVICE_CLASS_BATTERY
 from homeassistant.core import callback
 from homeassistant.helpers.dispatcher import async_dispatcher_connect
 from homeassistant.helpers.entity import Entity
+from homeassistant.util.dt import utc_from_timestamp, utcnow
 
 from . import DOMAIN
 
@@ -58,6 +59,29 @@ class GeniusDevice(Entity):
         """Return the name of the sensor."""
         return self._name
 
+    @property
+    def icon(self):
+        """Return the icon of the sensor."""
+        values = self._device._info_raw['childValues']  # noqa; pylint: disable=protected-access
+
+        last_comms = utc_from_timestamp(values['lastComms']['val'])
+        interval = timedelta(seconds=values['WakeUp_Interval']['val'])
+
+        if last_comms < utcnow() - interval * 3:
+            return 'mdi:battery-unknown'
+
+        battery_level = self._device.state['batteryLevel']
+        if battery_level == 255:
+            return 'mdi:battery-unknown'
+        if battery_level < 40:
+            return 'mdi:battery-alert'
+
+        icon = 'mdi:battery'
+        if battery_level <= 95:
+            icon += '-{}'.format(int(round(battery_level / 10 - .01)) * 10)
+
+        return icon
+
     @property
     def device_class(self):
         """Return the device class of the sensor."""
@@ -86,8 +110,7 @@ class GeniusDevice(Entity):
         attrs['assigned_zone'] = self._device.assignedZones[0]['name']
 
         last_comms = self._device._info_raw['childValues']['lastComms']['val']  # noqa; pylint: disable=protected-access
-        attrs['last_comms'] = datetime.utcfromtimestamp(
-            last_comms).isoformat()
+        attrs['last_comms'] = utc_from_timestamp(last_comms).isoformat()
 
         return {**attrs}