diff --git a/homeassistant/components/homekit/__init__.py b/homeassistant/components/homekit/__init__.py
index 59c227fb0b8..1c30de918e3 100644
--- a/homeassistant/components/homekit/__init__.py
+++ b/homeassistant/components/homekit/__init__.py
@@ -78,7 +78,7 @@ async def async_setup(hass, config):
 
     homekit = HomeKit(hass, name, port, ip_address, entity_filter,
                       entity_config)
-    await hass.async_add_job(homekit.setup)
+    await hass.async_add_executor_job(homekit.setup)
 
     if auto_start:
         hass.bus.async_listen_once(EVENT_HOMEASSISTANT_START, homekit.start)
diff --git a/homeassistant/components/homekit/accessories.py b/homeassistant/components/homekit/accessories.py
index 2c41885e311..5baed0294b8 100644
--- a/homeassistant/components/homekit/accessories.py
+++ b/homeassistant/components/homekit/accessories.py
@@ -35,7 +35,7 @@ def debounce(func):
         """Handle call_later callback."""
         debounce_params = self.debounce.pop(func.__name__, None)
         if debounce_params:
-            self.hass.async_add_job(func, self, *debounce_params[1:])
+            self.hass.async_add_executor_job(func, self, *debounce_params[1:])
 
     @wraps(func)
     def wrapper(self, *args):
@@ -94,8 +94,15 @@ class HomeAccessory(Accessory):
 
         Run inside the HAP-python event loop.
         """
+        self.hass.add_job(self.run_handler)
+
+    async def run_handler(self):
+        """Handle accessory driver started event.
+
+        Run inside the Home Assistant event loop.
+        """
         state = self.hass.states.get(self.entity_id)
-        self.hass.add_job(self.update_state_callback, None, None, state)
+        self.hass.async_add_job(self.update_state_callback, None, None, state)
         async_track_state_change(
             self.hass, self.entity_id, self.update_state_callback)
 
@@ -107,8 +114,8 @@ class HomeAccessory(Accessory):
         if new_state is None:
             return
         if self._support_battery_level:
-            self.hass.async_add_job(self.update_battery, new_state)
-        self.hass.async_add_job(self.update_state, new_state)
+            self.hass.async_add_executor_job(self.update_battery, new_state)
+        self.hass.async_add_executor_job(self.update_state, new_state)
 
     def update_battery(self, new_state):
         """Update battery service if available.
diff --git a/homeassistant/components/homekit/type_covers.py b/homeassistant/components/homekit/type_covers.py
index 787e0e52b1d..840800f730b 100644
--- a/homeassistant/components/homekit/type_covers.py
+++ b/homeassistant/components/homekit/type_covers.py
@@ -31,7 +31,7 @@ class GarageDoorOpener(HomeAccessory):
     def __init__(self, *args):
         """Initialize a GarageDoorOpener accessory object."""
         super().__init__(*args, category=CATEGORY_GARAGE_DOOR_OPENER)
-        self.flag_target_state = False
+        self._flag_state = False
 
         serv_garage_door = self.add_preload_service(SERV_GARAGE_DOOR_OPENER)
         self.char_current_state = serv_garage_door.configure_char(
@@ -42,7 +42,7 @@ class GarageDoorOpener(HomeAccessory):
     def set_state(self, value):
         """Change garage state if call came from HomeKit."""
         _LOGGER.debug('%s: Set state to %d', self.entity_id, value)
-        self.flag_target_state = True
+        self._flag_state = True
 
         params = {ATTR_ENTITY_ID: self.entity_id}
         if value == 0:
@@ -58,9 +58,9 @@ class GarageDoorOpener(HomeAccessory):
         if hass_state in (STATE_OPEN, STATE_CLOSED):
             current_state = 0 if hass_state == STATE_OPEN else 1
             self.char_current_state.set_value(current_state)
-            if not self.flag_target_state:
+            if not self._flag_state:
                 self.char_target_state.set_value(current_state)
-            self.flag_target_state = False
+            self._flag_state = False
 
 
 @TYPES.register('WindowCovering')
@@ -73,7 +73,7 @@ class WindowCovering(HomeAccessory):
     def __init__(self, *args):
         """Initialize a WindowCovering accessory object."""
         super().__init__(*args, category=CATEGORY_WINDOW_COVERING)
-        self.homekit_target = None
+        self._homekit_target = None
 
         serv_cover = self.add_preload_service(SERV_WINDOW_COVERING)
         self.char_current_position = serv_cover.configure_char(
@@ -85,7 +85,7 @@ class WindowCovering(HomeAccessory):
     def move_cover(self, value):
         """Move cover to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set position to %d', self.entity_id, value)
-        self.homekit_target = value
+        self._homekit_target = value
 
         params = {ATTR_ENTITY_ID: self.entity_id, ATTR_POSITION: value}
         self.call_service(DOMAIN, SERVICE_SET_COVER_POSITION, params, value)
@@ -95,10 +95,10 @@ class WindowCovering(HomeAccessory):
         current_position = new_state.attributes.get(ATTR_CURRENT_POSITION)
         if isinstance(current_position, int):
             self.char_current_position.set_value(current_position)
-            if self.homekit_target is None or \
-                    abs(current_position - self.homekit_target) < 6:
+            if self._homekit_target is None or \
+                    abs(current_position - self._homekit_target) < 6:
                 self.char_target_position.set_value(current_position)
-                self.homekit_target = None
+                self._homekit_target = None
 
 
 @TYPES.register('WindowCoveringBasic')
@@ -114,7 +114,7 @@ class WindowCoveringBasic(HomeAccessory):
         super().__init__(*args, category=CATEGORY_WINDOW_COVERING)
         features = self.hass.states.get(self.entity_id) \
             .attributes.get(ATTR_SUPPORTED_FEATURES)
-        self.supports_stop = features & SUPPORT_STOP
+        self._supports_stop = features & SUPPORT_STOP
 
         serv_cover = self.add_preload_service(SERV_WINDOW_COVERING)
         self.char_current_position = serv_cover.configure_char(
@@ -129,7 +129,7 @@ class WindowCoveringBasic(HomeAccessory):
         """Move cover to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set position to %d', self.entity_id, value)
 
-        if self.supports_stop:
+        if self._supports_stop:
             if value > 70:
                 service, position = (SERVICE_OPEN_COVER, 100)
             elif value < 30:
diff --git a/homeassistant/components/homekit/type_fans.py b/homeassistant/components/homekit/type_fans.py
index 49eb525aa51..5a860ed21c8 100644
--- a/homeassistant/components/homekit/type_fans.py
+++ b/homeassistant/components/homekit/type_fans.py
@@ -34,24 +34,27 @@ class Fan(HomeAccessory):
                       CHAR_SWING_MODE: False}
         self._state = 0
 
-        self.chars = []
+        chars = []
         features = self.hass.states.get(self.entity_id) \
             .attributes.get(ATTR_SUPPORTED_FEATURES)
         if features & SUPPORT_DIRECTION:
-            self.chars.append(CHAR_ROTATION_DIRECTION)
+            chars.append(CHAR_ROTATION_DIRECTION)
         if features & SUPPORT_OSCILLATE:
-            self.chars.append(CHAR_SWING_MODE)
+            chars.append(CHAR_SWING_MODE)
 
-        serv_fan = self.add_preload_service(SERV_FANV2, self.chars)
+        serv_fan = self.add_preload_service(SERV_FANV2, chars)
         self.char_active = serv_fan.configure_char(
             CHAR_ACTIVE, value=0, setter_callback=self.set_state)
 
-        if CHAR_ROTATION_DIRECTION in self.chars:
+        self.char_direction = None
+        self.char_swing = None
+
+        if CHAR_ROTATION_DIRECTION in chars:
             self.char_direction = serv_fan.configure_char(
                 CHAR_ROTATION_DIRECTION, value=0,
                 setter_callback=self.set_direction)
 
-        if CHAR_SWING_MODE in self.chars:
+        if CHAR_SWING_MODE in chars:
             self.char_swing = serv_fan.configure_char(
                 CHAR_SWING_MODE, value=0, setter_callback=self.set_oscillating)
 
@@ -92,7 +95,7 @@ class Fan(HomeAccessory):
             self._flag[CHAR_ACTIVE] = False
 
         # Handle Direction
-        if CHAR_ROTATION_DIRECTION in self.chars:
+        if self.char_direction is not None:
             direction = new_state.attributes.get(ATTR_DIRECTION)
             if not self._flag[CHAR_ROTATION_DIRECTION] and \
                     direction in (DIRECTION_FORWARD, DIRECTION_REVERSE):
@@ -102,7 +105,7 @@ class Fan(HomeAccessory):
             self._flag[CHAR_ROTATION_DIRECTION] = False
 
         # Handle Oscillating
-        if CHAR_SWING_MODE in self.chars:
+        if self.char_swing is not None:
             oscillating = new_state.attributes.get(ATTR_OSCILLATING)
             if not self._flag[CHAR_SWING_MODE] and \
                     oscillating in (True, False):
diff --git a/homeassistant/components/homekit/type_lights.py b/homeassistant/components/homekit/type_lights.py
index b8125e24eba..a9007ace35b 100644
--- a/homeassistant/components/homekit/type_lights.py
+++ b/homeassistant/components/homekit/type_lights.py
@@ -95,7 +95,7 @@ class Light(HomeAccessory):
             return
         params = {ATTR_ENTITY_ID: self.entity_id, ATTR_BRIGHTNESS_PCT: value}
         self.call_service(DOMAIN, SERVICE_TURN_ON, params,
-                          "brightness at {}%".format(value))
+                          'brightness at {}%'.format(value))
 
     def set_color_temperature(self, value):
         """Set color temperature if call came from HomeKit."""
@@ -103,7 +103,7 @@ class Light(HomeAccessory):
         self._flag[CHAR_COLOR_TEMPERATURE] = True
         params = {ATTR_ENTITY_ID: self.entity_id, ATTR_COLOR_TEMP: value}
         self.call_service(DOMAIN, SERVICE_TURN_ON, params,
-                          "color temperature at {}".format(value))
+                          'color temperature at {}'.format(value))
 
     def set_saturation(self, value):
         """Set saturation if call came from HomeKit."""
@@ -129,7 +129,7 @@ class Light(HomeAccessory):
                 CHAR_HUE: False, CHAR_SATURATION: False, RGB_COLOR: True})
             params = {ATTR_ENTITY_ID: self.entity_id, ATTR_HS_COLOR: color}
             self.call_service(DOMAIN, SERVICE_TURN_ON, params,
-                              "set color at {}".format(color))
+                              'set color at {}'.format(color))
 
     def update_state(self, new_state):
         """Update light after state change."""
diff --git a/homeassistant/components/homekit/type_locks.py b/homeassistant/components/homekit/type_locks.py
index a3d9c3b6fac..fb211617ecf 100644
--- a/homeassistant/components/homekit/type_locks.py
+++ b/homeassistant/components/homekit/type_locks.py
@@ -33,7 +33,7 @@ class Lock(HomeAccessory):
         """Initialize a Lock accessory object."""
         super().__init__(*args, category=CATEGORY_DOOR_LOCK)
         self._code = self.config.get(ATTR_CODE)
-        self.flag_target_state = False
+        self._flag_state = False
 
         serv_lock_mechanism = self.add_preload_service(SERV_LOCK)
         self.char_current_state = serv_lock_mechanism.configure_char(
@@ -45,8 +45,8 @@ class Lock(HomeAccessory):
 
     def set_state(self, value):
         """Set lock state to value if call came from HomeKit."""
-        _LOGGER.debug("%s: Set state to %d", self.entity_id, value)
-        self.flag_target_state = True
+        _LOGGER.debug('%s: Set state to %d', self.entity_id, value)
+        self._flag_state = True
 
         hass_value = HOMEKIT_TO_HASS.get(value)
         service = STATE_TO_SERVICE[hass_value]
@@ -67,6 +67,6 @@ class Lock(HomeAccessory):
 
             # LockTargetState only supports locked and unlocked
             if hass_state in (STATE_LOCKED, STATE_UNLOCKED):
-                if not self.flag_target_state:
+                if not self._flag_state:
                     self.char_target_state.set_value(current_lock_state)
-                self.flag_target_state = False
+                self._flag_state = False
diff --git a/homeassistant/components/homekit/type_security_systems.py b/homeassistant/components/homekit/type_security_systems.py
index 206da3e2889..e210217df2f 100644
--- a/homeassistant/components/homekit/type_security_systems.py
+++ b/homeassistant/components/homekit/type_security_systems.py
@@ -39,7 +39,7 @@ class SecuritySystem(HomeAccessory):
         """Initialize a SecuritySystem accessory object."""
         super().__init__(*args, category=CATEGORY_ALARM_SYSTEM)
         self._alarm_code = self.config.get(ATTR_CODE)
-        self.flag_target_state = False
+        self._flag_state = False
 
         serv_alarm = self.add_preload_service(SERV_SECURITY_SYSTEM)
         self.char_current_state = serv_alarm.configure_char(
@@ -52,7 +52,7 @@ class SecuritySystem(HomeAccessory):
         """Move security state to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set security state to %d',
                       self.entity_id, value)
-        self.flag_target_state = True
+        self._flag_state = True
         hass_value = HOMEKIT_TO_HASS[value]
         service = STATE_TO_SERVICE[hass_value]
 
@@ -71,7 +71,7 @@ class SecuritySystem(HomeAccessory):
                           self.entity_id, hass_state, current_security_state)
 
             # SecuritySystemTargetState does not support triggered
-            if not self.flag_target_state and \
+            if not self._flag_state and \
                     hass_state != STATE_ALARM_TRIGGERED:
                 self.char_target_state.set_value(current_security_state)
-            self.flag_target_state = False
+            self._flag_state = False
diff --git a/homeassistant/components/homekit/type_sensors.py b/homeassistant/components/homekit/type_sensors.py
index d2101b1e6f9..09da361ddb8 100644
--- a/homeassistant/components/homekit/type_sensors.py
+++ b/homeassistant/components/homekit/type_sensors.py
@@ -58,7 +58,6 @@ class TemperatureSensor(HomeAccessory):
         serv_temp = self.add_preload_service(SERV_TEMPERATURE_SENSOR)
         self.char_temp = serv_temp.configure_char(
             CHAR_CURRENT_TEMPERATURE, value=0, properties=PROP_CELSIUS)
-        self.unit = None
 
     def update_state(self, new_state):
         """Update temperature after state changed."""
diff --git a/homeassistant/components/homekit/type_switches.py b/homeassistant/components/homekit/type_switches.py
index 1090205ff56..59ae17b5d9d 100644
--- a/homeassistant/components/homekit/type_switches.py
+++ b/homeassistant/components/homekit/type_switches.py
@@ -36,7 +36,7 @@ class Outlet(HomeAccessory):
     def __init__(self, *args):
         """Initialize an Outlet accessory object."""
         super().__init__(*args, category=CATEGORY_OUTLET)
-        self.flag_target_state = False
+        self._flag_state = False
 
         serv_outlet = self.add_preload_service(SERV_OUTLET)
         self.char_on = serv_outlet.configure_char(
@@ -48,7 +48,7 @@ class Outlet(HomeAccessory):
         """Move switch state to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set switch state to %s',
                       self.entity_id, value)
-        self.flag_target_state = True
+        self._flag_state = True
         params = {ATTR_ENTITY_ID: self.entity_id}
         service = SERVICE_TURN_ON if value else SERVICE_TURN_OFF
         self.call_service(DOMAIN, service, params)
@@ -56,11 +56,11 @@ class Outlet(HomeAccessory):
     def update_state(self, new_state):
         """Update switch state after state changed."""
         current_state = (new_state.state == STATE_ON)
-        if not self.flag_target_state:
+        if not self._flag_state:
             _LOGGER.debug('%s: Set current state to %s',
                           self.entity_id, current_state)
             self.char_on.set_value(current_state)
-        self.flag_target_state = False
+        self._flag_state = False
 
 
 @TYPES.register('Switch')
@@ -71,7 +71,7 @@ class Switch(HomeAccessory):
         """Initialize a Switch accessory object."""
         super().__init__(*args, category=CATEGORY_SWITCH)
         self._domain = split_entity_id(self.entity_id)[0]
-        self.flag_target_state = False
+        self._flag_state = False
 
         serv_switch = self.add_preload_service(SERV_SWITCH)
         self.char_on = serv_switch.configure_char(
@@ -81,7 +81,7 @@ class Switch(HomeAccessory):
         """Move switch state to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set switch state to %s',
                       self.entity_id, value)
-        self.flag_target_state = True
+        self._flag_state = True
         params = {ATTR_ENTITY_ID: self.entity_id}
         service = SERVICE_TURN_ON if value else SERVICE_TURN_OFF
         self.call_service(self._domain, service, params)
@@ -89,11 +89,11 @@ class Switch(HomeAccessory):
     def update_state(self, new_state):
         """Update switch state after state changed."""
         current_state = (new_state.state == STATE_ON)
-        if not self.flag_target_state:
+        if not self._flag_state:
             _LOGGER.debug('%s: Set current state to %s',
                           self.entity_id, current_state)
             self.char_on.set_value(current_state)
-        self.flag_target_state = False
+        self._flag_state = False
 
 
 @TYPES.register('Valve')
@@ -103,7 +103,7 @@ class Valve(HomeAccessory):
     def __init__(self, *args):
         """Initialize a Valve accessory object."""
         super().__init__(*args)
-        self.flag_target_state = False
+        self._flag_state = False
         valve_type = self.config[CONF_TYPE]
         self.category = VALVE_TYPE[valve_type][0]
 
@@ -119,7 +119,7 @@ class Valve(HomeAccessory):
         """Move value state to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set switch state to %s',
                       self.entity_id, value)
-        self.flag_target_state = True
+        self._flag_state = True
         self.char_in_use.set_value(value)
         params = {ATTR_ENTITY_ID: self.entity_id}
         service = SERVICE_TURN_ON if value else SERVICE_TURN_OFF
@@ -128,9 +128,9 @@ class Valve(HomeAccessory):
     def update_state(self, new_state):
         """Update switch state after state changed."""
         current_state = (new_state.state == STATE_ON)
-        if not self.flag_target_state:
+        if not self._flag_state:
             _LOGGER.debug('%s: Set current state to %s',
                           self.entity_id, current_state)
             self.char_active.set_value(current_state)
             self.char_in_use.set_value(current_state)
-        self.flag_target_state = False
+        self._flag_state = False
diff --git a/homeassistant/components/homekit/type_thermostats.py b/homeassistant/components/homekit/type_thermostats.py
index 2513ee50981..49da6db6125 100644
--- a/homeassistant/components/homekit/type_thermostats.py
+++ b/homeassistant/components/homekit/type_thermostats.py
@@ -51,11 +51,11 @@ class Thermostat(HomeAccessory):
         """Initialize a Thermostat accessory object."""
         super().__init__(*args, category=CATEGORY_THERMOSTAT)
         self._unit = self.hass.config.units.temperature_unit
+        self._flag_heat_cool = False
+        self._flag_temperature = False
+        self._flag_coolingthresh = False
+        self._flag_heatingthresh = False
         self.support_power_state = False
-        self.heat_cool_flag_target_state = False
-        self.temperature_flag_target_state = False
-        self.coolingthresh_flag_target_state = False
-        self.heatingthresh_flag_target_state = False
         min_temp, max_temp = self.get_temperature_range()
 
         # Add additional characteristics if auto mode is supported
@@ -122,28 +122,27 @@ class Thermostat(HomeAccessory):
 
     def set_heat_cool(self, value):
         """Change operation mode to value if call came from HomeKit."""
-        if value in HC_HOMEKIT_TO_HASS:
-            _LOGGER.debug('%s: Set heat-cool to %d', self.entity_id, value)
-            self.heat_cool_flag_target_state = True
-            hass_value = HC_HOMEKIT_TO_HASS[value]
-            if self.support_power_state is True:
-                params = {ATTR_ENTITY_ID: self.entity_id}
-                if hass_value == STATE_OFF:
-                    self.call_service(DOMAIN_CLIMATE, SERVICE_TURN_OFF, params)
-                    return
-                self.call_service(DOMAIN_CLIMATE, SERVICE_TURN_ON, params)
-            params = {ATTR_ENTITY_ID: self.entity_id,
-                      ATTR_OPERATION_MODE: hass_value}
-            self.call_service(
-                DOMAIN_CLIMATE, SERVICE_SET_OPERATION_MODE_THERMOSTAT,
-                params, hass_value)
+        _LOGGER.debug('%s: Set heat-cool to %d', self.entity_id, value)
+        self._flag_heat_cool = True
+        hass_value = HC_HOMEKIT_TO_HASS[value]
+        if self.support_power_state is True:
+            params = {ATTR_ENTITY_ID: self.entity_id}
+            if hass_value == STATE_OFF:
+                self.call_service(DOMAIN_CLIMATE, SERVICE_TURN_OFF, params)
+                return
+            self.call_service(DOMAIN_CLIMATE, SERVICE_TURN_ON, params)
+        params = {ATTR_ENTITY_ID: self.entity_id,
+                  ATTR_OPERATION_MODE: hass_value}
+        self.call_service(
+            DOMAIN_CLIMATE, SERVICE_SET_OPERATION_MODE_THERMOSTAT,
+            params, hass_value)
 
     @debounce
     def set_cooling_threshold(self, value):
         """Set cooling threshold temp to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set cooling threshold temperature to %.2f°C',
                       self.entity_id, value)
-        self.coolingthresh_flag_target_state = True
+        self._flag_coolingthresh = True
         low = self.char_heating_thresh_temp.value
         temperature = temperature_to_states(value, self._unit)
         params = {
@@ -159,7 +158,7 @@ class Thermostat(HomeAccessory):
         """Set heating threshold temp to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set heating threshold temperature to %.2f°C',
                       self.entity_id, value)
-        self.heatingthresh_flag_target_state = True
+        self._flag_heatingthresh = True
         high = self.char_cooling_thresh_temp.value
         temperature = temperature_to_states(value, self._unit)
         params = {
@@ -175,14 +174,14 @@ class Thermostat(HomeAccessory):
         """Set target temperature to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set target temperature to %.2f°C',
                       self.entity_id, value)
-        self.temperature_flag_target_state = True
+        self._flag_temperature = True
         temperature = temperature_to_states(value, self._unit)
         params = {
             ATTR_ENTITY_ID: self.entity_id,
             ATTR_TEMPERATURE: temperature}
         self.call_service(
             DOMAIN_CLIMATE, SERVICE_SET_TEMPERATURE_THERMOSTAT,
-            params, 'target {}{}'.format(temperature, self._unit))
+            params, '{}{}'.format(temperature, self._unit))
 
     def update_state(self, new_state):
         """Update thermostat state after state changed."""
@@ -196,9 +195,9 @@ class Thermostat(HomeAccessory):
         target_temp = new_state.attributes.get(ATTR_TEMPERATURE)
         if isinstance(target_temp, (int, float)):
             target_temp = temperature_to_homekit(target_temp, self._unit)
-            if not self.temperature_flag_target_state:
+            if not self._flag_temperature:
                 self.char_target_temp.set_value(target_temp)
-        self.temperature_flag_target_state = False
+        self._flag_temperature = False
 
         # Update cooling threshold temperature if characteristic exists
         if self.char_cooling_thresh_temp:
@@ -206,9 +205,9 @@ class Thermostat(HomeAccessory):
             if isinstance(cooling_thresh, (int, float)):
                 cooling_thresh = temperature_to_homekit(cooling_thresh,
                                                         self._unit)
-                if not self.coolingthresh_flag_target_state:
+                if not self._flag_coolingthresh:
                     self.char_cooling_thresh_temp.set_value(cooling_thresh)
-        self.coolingthresh_flag_target_state = False
+        self._flag_coolingthresh = False
 
         # Update heating threshold temperature if characteristic exists
         if self.char_heating_thresh_temp:
@@ -216,9 +215,9 @@ class Thermostat(HomeAccessory):
             if isinstance(heating_thresh, (int, float)):
                 heating_thresh = temperature_to_homekit(heating_thresh,
                                                         self._unit)
-                if not self.heatingthresh_flag_target_state:
+                if not self._flag_heatingthresh:
                     self.char_heating_thresh_temp.set_value(heating_thresh)
-        self.heatingthresh_flag_target_state = False
+        self._flag_heatingthresh = False
 
         # Update display units
         if self._unit and self._unit in UNIT_HASS_TO_HOMEKIT:
@@ -227,13 +226,12 @@ class Thermostat(HomeAccessory):
         # Update target operation mode
         operation_mode = new_state.attributes.get(ATTR_OPERATION_MODE)
         if self.support_power_state is True and new_state.state == STATE_OFF:
-            self.char_target_heat_cool.set_value(
-                HC_HASS_TO_HOMEKIT[STATE_OFF])
+            self.char_target_heat_cool.set_value(0)  # Off
         elif operation_mode and operation_mode in HC_HASS_TO_HOMEKIT:
-            if not self.heat_cool_flag_target_state:
+            if not self._flag_heat_cool:
                 self.char_target_heat_cool.set_value(
                     HC_HASS_TO_HOMEKIT[operation_mode])
-        self.heat_cool_flag_target_state = False
+        self._flag_heat_cool = False
 
         # Set current operation mode based on temperatures and target mode
         if self.support_power_state is True and new_state.state == STATE_OFF:
@@ -286,8 +284,8 @@ class WaterHeater(HomeAccessory):
         """Initialize a WaterHeater accessory object."""
         super().__init__(*args, category=CATEGORY_THERMOSTAT)
         self._unit = self.hass.config.units.temperature_unit
-        self.flag_heat_cool = False
-        self.flag_temperature = False
+        self._flag_heat_cool = False
+        self._flag_temperature = False
         min_temp, max_temp = self.get_temperature_range()
 
         serv_thermostat = self.add_preload_service(SERV_THERMOSTAT)
@@ -326,7 +324,7 @@ class WaterHeater(HomeAccessory):
     def set_heat_cool(self, value):
         """Change operation mode to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set heat-cool to %d', self.entity_id, value)
-        self.flag_heat_cool = True
+        self._flag_heat_cool = True
         hass_value = HC_HOMEKIT_TO_HASS[value]
         if hass_value != STATE_HEAT:
             self.char_target_heat_cool.set_value(1)  # Heat
@@ -336,14 +334,14 @@ class WaterHeater(HomeAccessory):
         """Set target temperature to value if call came from HomeKit."""
         _LOGGER.debug('%s: Set target temperature to %.2f°C',
                       self.entity_id, value)
-        self.flag_temperature = True
+        self._flag_temperature = True
         temperature = temperature_to_states(value, self._unit)
         params = {
             ATTR_ENTITY_ID: self.entity_id,
             ATTR_TEMPERATURE: temperature}
         self.call_service(
             DOMAIN_WATER_HEATER, SERVICE_SET_TEMPERATURE_WATER_HEATER,
-            params, 'target {}{}'.format(temperature, self._unit))
+            params, '{}{}'.format(temperature, self._unit))
 
     def update_state(self, new_state):
         """Update water_heater state after state change."""
@@ -352,9 +350,9 @@ class WaterHeater(HomeAccessory):
         if isinstance(temperature, (int, float)):
             temperature = temperature_to_homekit(temperature, self._unit)
             self.char_current_temp.set_value(temperature)
-            if not self.flag_temperature:
+            if not self._flag_temperature:
                 self.char_target_temp.set_value(temperature)
-        self.flag_temperature = False
+        self._flag_temperature = False
 
         # Update display units
         if self._unit and self._unit in UNIT_HASS_TO_HOMEKIT:
@@ -362,6 +360,6 @@ class WaterHeater(HomeAccessory):
 
         # Update target operation mode
         operation_mode = new_state.attributes.get(ATTR_OPERATION_MODE)
-        if operation_mode and not self.flag_heat_cool:
+        if operation_mode and not self._flag_heat_cool:
             self.char_target_heat_cool.set_value(1)  # Heat
-        self.flag_heat_cool = False
+        self._flag_heat_cool = False
diff --git a/homeassistant/components/homekit/util.py b/homeassistant/components/homekit/util.py
index 4dd7396cf8d..43ae4df3b50 100644
--- a/homeassistant/components/homekit/util.py
+++ b/homeassistant/components/homekit/util.py
@@ -104,7 +104,7 @@ def validate_media_player_features(state, feature_list):
             error_list.append(feature)
 
     if error_list:
-        _LOGGER.error("%s does not support features: %s",
+        _LOGGER.error('%s does not support features: %s',
                       state.entity_id, error_list)
         return False
     return True
diff --git a/tests/components/homekit/conftest.py b/tests/components/homekit/conftest.py
index 326845cf74f..95829435d0e 100644
--- a/tests/components/homekit/conftest.py
+++ b/tests/components/homekit/conftest.py
@@ -4,7 +4,7 @@ from unittest.mock import patch
 import pytest
 
 from homeassistant.components.homekit.const import EVENT_HOMEKIT_CHANGED
-from homeassistant.core import callback
+from homeassistant.core import callback as ha_callback
 
 from pyhap.accessory_driver import AccessoryDriver
 
@@ -25,5 +25,5 @@ def events(hass):
     events = []
     hass.bus.async_listen(
         EVENT_HOMEKIT_CHANGED,
-        callback(lambda e: events.append(e)))
+        ha_callback(lambda e: events.append(e)))
     yield events
diff --git a/tests/components/homekit/test_type_lights.py b/tests/components/homekit/test_type_lights.py
index 540d9a73f48..c540952017b 100644
--- a/tests/components/homekit/test_type_lights.py
+++ b/tests/components/homekit/test_type_lights.py
@@ -80,7 +80,6 @@ async def test_light_basic(hass, hk_driver, cls, events):
 async def test_light_brightness(hass, hk_driver, cls, events):
     """Test light with brightness."""
     entity_id = 'light.demo'
-    event_value = "brightness at "
 
     hass.states.async_set(entity_id, STATE_ON, {
         ATTR_SUPPORTED_FEATURES: SUPPORT_BRIGHTNESS, ATTR_BRIGHTNESS: 255})
@@ -108,7 +107,7 @@ async def test_light_brightness(hass, hk_driver, cls, events):
     assert call_turn_on[0].data[ATTR_ENTITY_ID] == entity_id
     assert call_turn_on[0].data[ATTR_BRIGHTNESS_PCT] == 20
     assert len(events) == 1
-    assert events[-1].data[ATTR_VALUE] == "{}20%".format(event_value)
+    assert events[-1].data[ATTR_VALUE] == 'brightness at 20%'
 
     await hass.async_add_job(acc.char_on.client_update_value, 1)
     await hass.async_add_job(acc.char_brightness.client_update_value, 40)
@@ -117,7 +116,7 @@ async def test_light_brightness(hass, hk_driver, cls, events):
     assert call_turn_on[1].data[ATTR_ENTITY_ID] == entity_id
     assert call_turn_on[1].data[ATTR_BRIGHTNESS_PCT] == 40
     assert len(events) == 2
-    assert events[-1].data[ATTR_VALUE] == "{}40%".format(event_value)
+    assert events[-1].data[ATTR_VALUE] == 'brightness at 40%'
 
     await hass.async_add_job(acc.char_on.client_update_value, 1)
     await hass.async_add_job(acc.char_brightness.client_update_value, 0)
@@ -154,7 +153,7 @@ async def test_light_color_temperature(hass, hk_driver, cls, events):
     assert call_turn_on[0].data[ATTR_ENTITY_ID] == entity_id
     assert call_turn_on[0].data[ATTR_COLOR_TEMP] == 250
     assert len(events) == 1
-    assert events[-1].data[ATTR_VALUE] == "color temperature at 250"
+    assert events[-1].data[ATTR_VALUE] == 'color temperature at 250'
 
 
 async def test_light_rgb_color(hass, hk_driver, cls, events):
@@ -185,4 +184,4 @@ async def test_light_rgb_color(hass, hk_driver, cls, events):
     assert call_turn_on[0].data[ATTR_ENTITY_ID] == entity_id
     assert call_turn_on[0].data[ATTR_HS_COLOR] == (145, 75)
     assert len(events) == 1
-    assert events[-1].data[ATTR_VALUE] == "set color at (145, 75)"
+    assert events[-1].data[ATTR_VALUE] == 'set color at (145, 75)'
diff --git a/tests/components/homekit/test_type_media_players.py b/tests/components/homekit/test_type_media_players.py
index 299570a6923..6b23b3cc58e 100644
--- a/tests/components/homekit/test_type_media_players.py
+++ b/tests/components/homekit/test_type_media_players.py
@@ -29,32 +29,32 @@ async def test_media_player_set_state(hass, hk_driver, events):
     assert acc.aid == 2
     assert acc.category == 8  # Switch
 
-    assert acc.chars[FEATURE_ON_OFF].value == 0
-    assert acc.chars[FEATURE_PLAY_PAUSE].value == 0
-    assert acc.chars[FEATURE_PLAY_STOP].value == 0
-    assert acc.chars[FEATURE_TOGGLE_MUTE].value == 0
+    assert acc.chars[FEATURE_ON_OFF].value is False
+    assert acc.chars[FEATURE_PLAY_PAUSE].value is False
+    assert acc.chars[FEATURE_PLAY_STOP].value is False
+    assert acc.chars[FEATURE_TOGGLE_MUTE].value is False
 
     hass.states.async_set(entity_id, STATE_ON, {ATTR_MEDIA_VOLUME_MUTED: True})
     await hass.async_block_till_done()
-    assert acc.chars[FEATURE_ON_OFF].value == 1
-    assert acc.chars[FEATURE_TOGGLE_MUTE].value == 1
+    assert acc.chars[FEATURE_ON_OFF].value is True
+    assert acc.chars[FEATURE_TOGGLE_MUTE].value is True
 
     hass.states.async_set(entity_id, STATE_OFF)
     await hass.async_block_till_done()
-    assert acc.chars[FEATURE_ON_OFF].value == 0
+    assert acc.chars[FEATURE_ON_OFF].value is False
 
     hass.states.async_set(entity_id, STATE_PLAYING)
     await hass.async_block_till_done()
-    assert acc.chars[FEATURE_PLAY_PAUSE].value == 1
-    assert acc.chars[FEATURE_PLAY_STOP].value == 1
+    assert acc.chars[FEATURE_PLAY_PAUSE].value is True
+    assert acc.chars[FEATURE_PLAY_STOP].value is True
 
     hass.states.async_set(entity_id, STATE_PAUSED)
     await hass.async_block_till_done()
-    assert acc.chars[FEATURE_PLAY_PAUSE].value == 0
+    assert acc.chars[FEATURE_PLAY_PAUSE].value is False
 
     hass.states.async_set(entity_id, STATE_IDLE)
     await hass.async_block_till_done()
-    assert acc.chars[FEATURE_PLAY_STOP].value == 0
+    assert acc.chars[FEATURE_PLAY_STOP].value is False
 
     # Set from HomeKit
     call_turn_on = async_mock_service(hass, DOMAIN, 'turn_on')
diff --git a/tests/components/homekit/test_type_thermostats.py b/tests/components/homekit/test_type_thermostats.py
index 73b27ca851c..795cb5db7d2 100644
--- a/tests/components/homekit/test_type_thermostats.py
+++ b/tests/components/homekit/test_type_thermostats.py
@@ -163,7 +163,7 @@ async def test_thermostat(hass, hk_driver, cls, events):
     assert call_set_temperature[0].data[ATTR_TEMPERATURE] == 19.0
     assert acc.char_target_temp.value == 19.0
     assert len(events) == 1
-    assert events[-1].data[ATTR_VALUE] == 'target 19.0°C'
+    assert events[-1].data[ATTR_VALUE] == '19.0°C'
 
     await hass.async_add_job(acc.char_target_heat_cool.client_update_value, 1)
     await hass.async_block_till_done()
@@ -379,7 +379,7 @@ async def test_thermostat_fahrenheit(hass, hk_driver, cls, events):
     assert call_set_temperature[2].data[ATTR_ENTITY_ID] == entity_id
     assert call_set_temperature[2].data[ATTR_TEMPERATURE] == 75.2
     assert len(events) == 3
-    assert events[-1].data[ATTR_VALUE] == 'target 75.2°F'
+    assert events[-1].data[ATTR_VALUE] == '75.2°F'
 
 
 async def test_thermostat_get_temperature_range(hass, hk_driver, cls):
@@ -453,7 +453,7 @@ async def test_water_heater(hass, hk_driver, cls, events):
     assert call_set_temperature[0].data[ATTR_TEMPERATURE] == 52.0
     assert acc.char_target_temp.value == 52.0
     assert len(events) == 1
-    assert events[-1].data[ATTR_VALUE] == 'target 52.0°C'
+    assert events[-1].data[ATTR_VALUE] == '52.0°C'
 
     await hass.async_add_job(acc.char_target_heat_cool.client_update_value, 0)
     await hass.async_block_till_done()
@@ -499,7 +499,7 @@ async def test_water_heater_fahrenheit(hass, hk_driver, cls, events):
     assert call_set_temperature[0].data[ATTR_TEMPERATURE] == 140.0
     assert acc.char_target_temp.value == 60.0
     assert len(events) == 1
-    assert events[-1].data[ATTR_VALUE] == 'target 140.0°F'
+    assert events[-1].data[ATTR_VALUE] == '140.0°F'
 
 
 async def test_water_heater_get_temperature_range(hass, hk_driver, cls):