diff --git a/homeassistant/components/oem/climate.py b/homeassistant/components/oem/climate.py
index babd93953db..846113fb586 100644
--- a/homeassistant/components/oem/climate.py
+++ b/homeassistant/components/oem/climate.py
@@ -5,18 +5,11 @@ from oemthermostat import Thermostat
 import requests
 import voluptuous as vol
 
-from homeassistant.components.climate import (
-    PLATFORM_SCHEMA,
-    ClimateEntity,
-    ClimateEntityFeature,
-)
+from homeassistant.components.climate import PLATFORM_SCHEMA, ClimateEntity
 from homeassistant.components.climate.const import (
-    CURRENT_HVAC_HEAT,
-    CURRENT_HVAC_IDLE,
-    CURRENT_HVAC_OFF,
-    HVAC_MODE_AUTO,
-    HVAC_MODE_HEAT,
-    HVAC_MODE_OFF,
+    ClimateEntityFeature,
+    HVACAction,
+    HVACMode,
 )
 from homeassistant.const import (
     ATTR_TEMPERATURE,
@@ -42,7 +35,7 @@ PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend(
     }
 )
 
-SUPPORT_HVAC = [HVAC_MODE_AUTO, HVAC_MODE_HEAT, HVAC_MODE_OFF]
+SUPPORT_HVAC = [HVACMode.AUTO, HVACMode.HEAT, HVACMode.OFF]
 
 
 def setup_platform(
@@ -69,6 +62,7 @@ def setup_platform(
 class ThermostatDevice(ClimateEntity):
     """Interface class for the oemthermostat module."""
 
+    _attr_hvac_modes = SUPPORT_HVAC
     _attr_supported_features = ClimateEntityFeature.TARGET_TEMPERATURE
 
     def __init__(self, thermostat, name):
@@ -83,24 +77,16 @@ class ThermostatDevice(ClimateEntity):
         self._mode = None
 
     @property
-    def hvac_mode(self):
+    def hvac_mode(self) -> HVACMode:
         """Return hvac operation ie. heat, cool mode.
 
         Need to be one of HVAC_MODE_*.
         """
         if self._mode == 2:
-            return HVAC_MODE_HEAT
+            return HVACMode.HEAT
         if self._mode == 1:
-            return HVAC_MODE_AUTO
-        return HVAC_MODE_OFF
-
-    @property
-    def hvac_modes(self):
-        """Return the list of available hvac operation modes.
-
-        Need to be a subset of HVAC_MODES.
-        """
-        return SUPPORT_HVAC
+            return HVACMode.AUTO
+        return HVACMode.OFF
 
     @property
     def name(self):
@@ -113,13 +99,13 @@ class ThermostatDevice(ClimateEntity):
         return TEMP_CELSIUS
 
     @property
-    def hvac_action(self):
+    def hvac_action(self) -> HVACAction:
         """Return current hvac i.e. heat, cool, idle."""
         if not self._mode:
-            return CURRENT_HVAC_OFF
+            return HVACAction.OFF
         if self._state:
-            return CURRENT_HVAC_HEAT
-        return CURRENT_HVAC_IDLE
+            return HVACAction.HEATING
+        return HVACAction.IDLE
 
     @property
     def current_temperature(self):
@@ -131,13 +117,13 @@ class ThermostatDevice(ClimateEntity):
         """Return the temperature we try to reach."""
         return self._setpoint
 
-    def set_hvac_mode(self, hvac_mode):
+    def set_hvac_mode(self, hvac_mode: HVACMode) -> None:
         """Set new target hvac mode."""
-        if hvac_mode == HVAC_MODE_AUTO:
+        if hvac_mode == HVACMode.AUTO:
             self.thermostat.mode = 1
-        elif hvac_mode == HVAC_MODE_HEAT:
+        elif hvac_mode == HVACMode.HEAT:
             self.thermostat.mode = 2
-        elif hvac_mode == HVAC_MODE_OFF:
+        elif hvac_mode == HVACMode.OFF:
             self.thermostat.mode = 0
 
     def set_temperature(self, **kwargs):