diff --git a/homeassistant/components/ambient_station/__init__.py b/homeassistant/components/ambient_station/__init__.py
index 12465dfd984..7343c2d21ed 100644
--- a/homeassistant/components/ambient_station/__init__.py
+++ b/homeassistant/components/ambient_station/__init__.py
@@ -13,6 +13,7 @@ from homeassistant.const import (
     CONCENTRATION_PARTS_PER_MILLION,
     CONF_API_KEY,
     EVENT_HOMEASSISTANT_STOP,
+    POWER_WATT,
     SPEED_MILES_PER_HOUR,
     TEMP_FAHRENHEIT,
     UNIT_PERCENTAGE,
@@ -200,7 +201,7 @@ SENSOR_TYPES = {
     TYPE_SOILTEMP7F: ("Soil Temp 7", TEMP_FAHRENHEIT, TYPE_SENSOR, "temperature"),
     TYPE_SOILTEMP8F: ("Soil Temp 8", TEMP_FAHRENHEIT, TYPE_SENSOR, "temperature"),
     TYPE_SOILTEMP9F: ("Soil Temp 9", TEMP_FAHRENHEIT, TYPE_SENSOR, "temperature"),
-    TYPE_SOLARRADIATION: ("Solar Rad", "W/m^2", TYPE_SENSOR, None),
+    TYPE_SOLARRADIATION: ("Solar Rad", f"{POWER_WATT}/m^2", TYPE_SENSOR, None),
     TYPE_SOLARRADIATION_LX: ("Solar Rad (lx)", "lx", TYPE_SENSOR, "illuminance"),
     TYPE_TEMP10F: ("Temp 10", TEMP_FAHRENHEIT, TYPE_SENSOR, "temperature"),
     TYPE_TEMP1F: ("Temp 1", TEMP_FAHRENHEIT, TYPE_SENSOR, "temperature"),
diff --git a/homeassistant/components/aqualogic/sensor.py b/homeassistant/components/aqualogic/sensor.py
index 74a70f0b11c..a53a8c1d348 100644
--- a/homeassistant/components/aqualogic/sensor.py
+++ b/homeassistant/components/aqualogic/sensor.py
@@ -6,6 +6,7 @@ import voluptuous as vol
 from homeassistant.components.sensor import PLATFORM_SCHEMA
 from homeassistant.const import (
     CONF_MONITORED_CONDITIONS,
+    POWER_WATT,
     TEMP_CELSIUS,
     TEMP_FAHRENHEIT,
     UNIT_PERCENTAGE,
@@ -21,7 +22,7 @@ _LOGGER = logging.getLogger(__name__)
 TEMP_UNITS = [TEMP_CELSIUS, TEMP_FAHRENHEIT]
 PERCENT_UNITS = [UNIT_PERCENTAGE, UNIT_PERCENTAGE]
 SALT_UNITS = ["g/L", "PPM"]
-WATT_UNITS = ["W", "W"]
+WATT_UNITS = [POWER_WATT, POWER_WATT]
 NO_UNITS = [None, None]
 
 # sensor_type [ description, unit, icon ]
diff --git a/homeassistant/components/bom/weather.py b/homeassistant/components/bom/weather.py
index 94b9960c851..139c61a3b0f 100644
--- a/homeassistant/components/bom/weather.py
+++ b/homeassistant/components/bom/weather.py
@@ -4,7 +4,13 @@ import logging
 import voluptuous as vol
 
 from homeassistant.components.weather import PLATFORM_SCHEMA, WeatherEntity
-from homeassistant.const import CONF_LATITUDE, CONF_LONGITUDE, CONF_NAME, TEMP_CELSIUS
+from homeassistant.const import (
+    CONF_LATITUDE,
+    CONF_LONGITUDE,
+    CONF_NAME,
+    POWER_WATT,
+    TEMP_CELSIUS,
+)
 from homeassistant.helpers import config_validation as cv
 
 # Reuse data and API logic from the sensor implementation
@@ -99,7 +105,7 @@ class BOMWeather(WeatherEntity):
             "SSW",
             "SW",
             "WSW",
-            "W",
+            POWER_WATT,
             "WNW",
             "NW",
             "NNW",
diff --git a/homeassistant/components/growatt_server/sensor.py b/homeassistant/components/growatt_server/sensor.py
index 6742b39e8b0..f51e38bd9da 100644
--- a/homeassistant/components/growatt_server/sensor.py
+++ b/homeassistant/components/growatt_server/sensor.py
@@ -13,6 +13,7 @@ from homeassistant.const import (
     CONF_PASSWORD,
     CONF_USERNAME,
     ENERGY_KILO_WATT_HOUR,
+    POWER_WATT,
     UNIT_VOLT,
 )
 import homeassistant.helpers.config_validation as cv
@@ -35,14 +36,14 @@ TOTAL_SENSOR_TYPES = {
         "todayEnergy",
         "power",
     ),
-    "total_output_power": ("Output Power", "W", "invTodayPpv", "power"),
+    "total_output_power": ("Output Power", POWER_WATT, "invTodayPpv", "power"),
     "total_energy_output": (
         "Lifetime energy output",
         ENERGY_KILO_WATT_HOUR,
         "totalEnergy",
         "power",
     ),
-    "total_maximum_output": ("Maximum power", "W", "nominalPower", "power"),
+    "total_maximum_output": ("Maximum power", POWER_WATT, "nominalPower", "power"),
 }
 
 INVERTER_SENSOR_TYPES = {
@@ -60,19 +61,24 @@ INVERTER_SENSOR_TYPES = {
     ),
     "inverter_voltage_input_1": ("Input 1 voltage", UNIT_VOLT, "vpv1", None),
     "inverter_amperage_input_1": ("Input 1 Amperage", "A", "ipv1", None),
-    "inverter_wattage_input_1": ("Input 1 Wattage", "W", "ppv1", "power"),
+    "inverter_wattage_input_1": ("Input 1 Wattage", POWER_WATT, "ppv1", "power"),
     "inverter_voltage_input_2": ("Input 2 voltage", UNIT_VOLT, "vpv2", None),
     "inverter_amperage_input_2": ("Input 2 Amperage", "A", "ipv2", None),
-    "inverter_wattage_input_2": ("Input 2 Wattage", "W", "ppv2", "power"),
+    "inverter_wattage_input_2": ("Input 2 Wattage", POWER_WATT, "ppv2", "power"),
     "inverter_voltage_input_3": ("Input 3 voltage", UNIT_VOLT, "vpv3", None),
     "inverter_amperage_input_3": ("Input 3 Amperage", "A", "ipv3", None),
-    "inverter_wattage_input_3": ("Input 3 Wattage", "W", "ppv3", "power"),
-    "inverter_internal_wattage": ("Internal wattage", "W", "ppv", "power"),
+    "inverter_wattage_input_3": ("Input 3 Wattage", POWER_WATT, "ppv3", "power"),
+    "inverter_internal_wattage": ("Internal wattage", POWER_WATT, "ppv", "power"),
     "inverter_reactive_voltage": ("Reactive voltage", UNIT_VOLT, "vacr", None),
     "inverter_inverter_reactive_amperage": ("Reactive amperage", "A", "iacr", None),
     "inverter_frequency": ("AC frequency", "Hz", "fac", None),
-    "inverter_current_wattage": ("Output power", "W", "pac", "power"),
-    "inverter_current_reactive_wattage": ("Reactive wattage", "W", "pacr", "power"),
+    "inverter_current_wattage": ("Output power", POWER_WATT, "pac", "power"),
+    "inverter_current_reactive_wattage": (
+        "Reactive wattage",
+        POWER_WATT,
+        "pacr",
+        "power",
+    ),
 }
 
 SENSOR_TYPES = {**TOTAL_SENSOR_TYPES, **INVERTER_SENSOR_TYPES}
diff --git a/homeassistant/components/homematicip_cloud/sensor.py b/homeassistant/components/homematicip_cloud/sensor.py
index a45591ecc30..e45e73b8c03 100644
--- a/homeassistant/components/homematicip_cloud/sensor.py
+++ b/homeassistant/components/homematicip_cloud/sensor.py
@@ -414,7 +414,7 @@ def _get_wind_direction(wind_direction_degree: float) -> str:
     if 236.25 <= wind_direction_degree < 258.75:
         return "WSW"
     if 258.75 <= wind_direction_degree < 281.25:
-        return "W"
+        return POWER_WATT
     if 281.25 <= wind_direction_degree < 303.75:
         return "WNW"
     if 303.75 <= wind_direction_degree < 326.25:
diff --git a/homeassistant/components/isy994/sensor.py b/homeassistant/components/isy994/sensor.py
index 47b9fc1d633..a52dcdbe09a 100644
--- a/homeassistant/components/isy994/sensor.py
+++ b/homeassistant/components/isy994/sensor.py
@@ -95,7 +95,7 @@ UOM_FRIENDLY_NAME = {
     "71": UNIT_UV_INDEX,
     "72": UNIT_VOLT,
     "73": POWER_WATT,
-    "74": "W/m²",
+    "74": f"{POWER_WATT}/m²",
     "75": "weekday",
     "76": "Wind Direction (°)",
     "77": TIME_YEARS,
diff --git a/homeassistant/components/solarlog/const.py b/homeassistant/components/solarlog/const.py
index b8512531f36..d89b175962e 100644
--- a/homeassistant/components/solarlog/const.py
+++ b/homeassistant/components/solarlog/const.py
@@ -83,7 +83,12 @@ SENSOR_TYPES = {
         "mdi:solar-power",
     ],
     "capacity": ["CAPACITY", "capacity", UNIT_PERCENTAGE, "mdi:solar-power"],
-    "efficiency": ["EFFICIENCY", "efficiency", "% W/Wp", "mdi:solar-power"],
+    "efficiency": [
+        "EFFICIENCY",
+        "efficiency",
+        f"% {POWER_WATT}/{POWER_WATT}p",
+        "mdi:solar-power",
+    ],
     "power_available": [
         "powerAVAILABLE",
         "power available",
diff --git a/homeassistant/components/tibber/sensor.py b/homeassistant/components/tibber/sensor.py
index 054fad3246a..36f1a65222c 100644
--- a/homeassistant/components/tibber/sensor.py
+++ b/homeassistant/components/tibber/sensor.py
@@ -5,6 +5,7 @@ import logging
 
 import aiohttp
 
+from homeassistant.const import POWER_WATT
 from homeassistant.exceptions import PlatformNotReady
 from homeassistant.helpers.entity import Entity
 from homeassistant.util import Throttle, dt as dt_util
@@ -194,7 +195,7 @@ class TibberSensorRT(TibberSensor):
     @property
     def unit_of_measurement(self):
         """Return the unit of measurement of this entity."""
-        return "W"
+        return POWER_WATT
 
     @property
     def unique_id(self):
diff --git a/homeassistant/components/waterfurnace/sensor.py b/homeassistant/components/waterfurnace/sensor.py
index b2b8aaa6f35..9378694f5f3 100644
--- a/homeassistant/components/waterfurnace/sensor.py
+++ b/homeassistant/components/waterfurnace/sensor.py
@@ -1,7 +1,7 @@
 """Support for Waterfurnace."""
 
 from homeassistant.components.sensor import ENTITY_ID_FORMAT
-from homeassistant.const import TEMP_FAHRENHEIT, UNIT_PERCENTAGE
+from homeassistant.const import POWER_WATT, TEMP_FAHRENHEIT, UNIT_PERCENTAGE
 from homeassistant.core import callback
 from homeassistant.helpers.entity import Entity
 from homeassistant.util import slugify
@@ -24,7 +24,7 @@ class WFSensorConfig:
 
 SENSORS = [
     WFSensorConfig("Furnace Mode", "mode"),
-    WFSensorConfig("Total Power", "totalunitpower", "mdi:flash", "W"),
+    WFSensorConfig("Total Power", "totalunitpower", "mdi:flash", POWER_WATT),
     WFSensorConfig(
         "Active Setpoint", "tstatactivesetpoint", "mdi:thermometer", TEMP_FAHRENHEIT
     ),
@@ -39,10 +39,10 @@ SENSORS = [
     WFSensorConfig(
         "Humidity", "tstatrelativehumidity", "mdi:water-percent", UNIT_PERCENTAGE
     ),
-    WFSensorConfig("Compressor Power", "compressorpower", "mdi:flash", "W"),
-    WFSensorConfig("Fan Power", "fanpower", "mdi:flash", "W"),
-    WFSensorConfig("Aux Power", "auxpower", "mdi:flash", "W"),
-    WFSensorConfig("Loop Pump Power", "looppumppower", "mdi:flash", "W"),
+    WFSensorConfig("Compressor Power", "compressorpower", "mdi:flash", POWER_WATT),
+    WFSensorConfig("Fan Power", "fanpower", "mdi:flash", POWER_WATT),
+    WFSensorConfig("Aux Power", "auxpower", "mdi:flash", POWER_WATT),
+    WFSensorConfig("Loop Pump Power", "looppumppower", "mdi:flash", POWER_WATT),
     WFSensorConfig("Compressor Speed", "actualcompressorspeed", "mdi:speedometer"),
     WFSensorConfig("Fan Speed", "airflowcurrentspeed", "mdi:fan"),
 ]
diff --git a/homeassistant/const.py b/homeassistant/const.py
index d69f0370720..0b8c3303358 100644
--- a/homeassistant/const.py
+++ b/homeassistant/const.py
@@ -349,8 +349,8 @@ POWER_WATT = "W"
 UNIT_VOLT = "V"
 
 # Energy units
-ENERGY_KILO_WATT_HOUR = "kWh"
-ENERGY_WATT_HOUR = "Wh"
+ENERGY_WATT_HOUR = f"{POWER_WATT}h"
+ENERGY_KILO_WATT_HOUR = f"k{ENERGY_WATT_HOUR}"
 
 # Temperature units
 TEMP_CELSIUS = "°C"
diff --git a/tests/components/derivative/test_sensor.py b/tests/components/derivative/test_sensor.py
index dc160b283ad..466f07a9deb 100644
--- a/tests/components/derivative/test_sensor.py
+++ b/tests/components/derivative/test_sensor.py
@@ -2,7 +2,7 @@
 from datetime import timedelta
 from unittest.mock import patch
 
-from homeassistant.const import TIME_HOURS, TIME_MINUTES, TIME_SECONDS
+from homeassistant.const import POWER_WATT, TIME_HOURS, TIME_MINUTES, TIME_SECONDS
 from homeassistant.setup import async_setup_component
 import homeassistant.util.dt as dt_util
 
@@ -192,14 +192,14 @@ async def test_prefix(hass):
 
     entity_id = config["sensor"]["source"]
     hass.states.async_set(
-        entity_id, 1000, {"unit_of_measurement": "W"}, force_update=True
+        entity_id, 1000, {"unit_of_measurement": POWER_WATT}, force_update=True
     )
     await hass.async_block_till_done()
 
     now = dt_util.utcnow() + timedelta(seconds=3600)
     with patch("homeassistant.util.dt.utcnow", return_value=now):
         hass.states.async_set(
-            entity_id, 1000, {"unit_of_measurement": "W"}, force_update=True
+            entity_id, 1000, {"unit_of_measurement": POWER_WATT}, force_update=True
         )
         await hass.async_block_till_done()
 
diff --git a/tests/components/homematicip_cloud/test_sensor.py b/tests/components/homematicip_cloud/test_sensor.py
index c55a4682216..61de66d916d 100644
--- a/tests/components/homematicip_cloud/test_sensor.py
+++ b/tests/components/homematicip_cloud/test_sensor.py
@@ -310,7 +310,7 @@ async def test_hmip_windspeed_sensor(hass, default_mock_hap_factory):
         205: "SSW",
         227.5: "SW",
         250: "WSW",
-        272.5: "W",
+        272.5: POWER_WATT,
         295: "WNW",
         317.5: "NW",
         340: "NNW",
diff --git a/tests/components/integration/test_sensor.py b/tests/components/integration/test_sensor.py
index ded0ab6bfad..3afa5c14c22 100644
--- a/tests/components/integration/test_sensor.py
+++ b/tests/components/integration/test_sensor.py
@@ -2,7 +2,7 @@
 from datetime import timedelta
 from unittest.mock import patch
 
-from homeassistant.const import ENERGY_KILO_WATT_HOUR, TIME_SECONDS
+from homeassistant.const import ENERGY_KILO_WATT_HOUR, POWER_WATT, TIME_SECONDS
 from homeassistant.setup import async_setup_component
 import homeassistant.util.dt as dt_util
 
@@ -155,13 +155,13 @@ async def test_prefix(hass):
     assert await async_setup_component(hass, "sensor", config)
 
     entity_id = config["sensor"]["source"]
-    hass.states.async_set(entity_id, 1000, {"unit_of_measurement": "W"})
+    hass.states.async_set(entity_id, 1000, {"unit_of_measurement": POWER_WATT})
     await hass.async_block_till_done()
 
     now = dt_util.utcnow() + timedelta(seconds=3600)
     with patch("homeassistant.util.dt.utcnow", return_value=now):
         hass.states.async_set(
-            entity_id, 1000, {"unit_of_measurement": "W"}, force_update=True
+            entity_id, 1000, {"unit_of_measurement": POWER_WATT}, force_update=True
         )
         await hass.async_block_till_done()
 
diff --git a/tests/components/zha/test_sensor.py b/tests/components/zha/test_sensor.py
index dbd2e8f7c3a..d560fe2cbba 100644
--- a/tests/components/zha/test_sensor.py
+++ b/tests/components/zha/test_sensor.py
@@ -14,6 +14,7 @@ from homeassistant.const import (
     CONF_UNIT_SYSTEM,
     CONF_UNIT_SYSTEM_IMPERIAL,
     CONF_UNIT_SYSTEM_METRIC,
+    POWER_WATT,
     STATE_UNAVAILABLE,
     STATE_UNKNOWN,
     TEMP_CELSIUS,
@@ -76,17 +77,17 @@ async def async_test_electrical_measurement(hass, cluster, entity_id):
     ) as divisor_mock:
         divisor_mock.return_value = 1
         await send_attributes_report(hass, cluster, {0: 1, 1291: 100, 10: 1000})
-        assert_state(hass, entity_id, "100", "W")
+        assert_state(hass, entity_id, "100", POWER_WATT)
 
         await send_attributes_report(hass, cluster, {0: 1, 1291: 99, 10: 1000})
-        assert_state(hass, entity_id, "99", "W")
+        assert_state(hass, entity_id, "99", POWER_WATT)
 
         divisor_mock.return_value = 10
         await send_attributes_report(hass, cluster, {0: 1, 1291: 1000, 10: 5000})
-        assert_state(hass, entity_id, "100", "W")
+        assert_state(hass, entity_id, "100", POWER_WATT)
 
         await send_attributes_report(hass, cluster, {0: 1, 1291: 99, 10: 5000})
-        assert_state(hass, entity_id, "9.9", "W")
+        assert_state(hass, entity_id, "9.9", POWER_WATT)
 
 
 @pytest.mark.parametrize(