diff --git a/homeassistant/components/apcupsd/sensor.py b/homeassistant/components/apcupsd/sensor.py
index 85bbe5c950e..6989f58d3bb 100644
--- a/homeassistant/components/apcupsd/sensor.py
+++ b/homeassistant/components/apcupsd/sensor.py
@@ -12,6 +12,7 @@ from homeassistant.const import (
     TIME_MINUTES,
     TIME_SECONDS,
     UNIT_PERCENTAGE,
+    UNIT_VOLT,
 )
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.entity import Entity
@@ -29,7 +30,7 @@ SENSOR_TYPES = {
     "badbatts": ["Bad Batteries", "", "mdi:information-outline"],
     "battdate": ["Battery Replaced", "", "mdi:calendar-clock"],
     "battstat": ["Battery Status", "", "mdi:information-outline"],
-    "battv": ["Battery Voltage", "V", "mdi:flash"],
+    "battv": ["Battery Voltage", UNIT_VOLT, "mdi:flash"],
     "bcharge": ["Battery", UNIT_PERCENTAGE, "mdi:battery"],
     "cable": ["Cable Type", "", "mdi:ethernet-cable"],
     "cumonbatt": ["Total Time on Battery", "", "mdi:timer"],
@@ -42,33 +43,33 @@ SENSOR_TYPES = {
     "endapc": ["Date and Time", "", "mdi:calendar-clock"],
     "extbatts": ["External Batteries", "", "mdi:information-outline"],
     "firmware": ["Firmware Version", "", "mdi:information-outline"],
-    "hitrans": ["Transfer High", "V", "mdi:flash"],
+    "hitrans": ["Transfer High", UNIT_VOLT, "mdi:flash"],
     "hostname": ["Hostname", "", "mdi:information-outline"],
     "humidity": ["Ambient Humidity", UNIT_PERCENTAGE, "mdi:water-percent"],
     "itemp": ["Internal Temperature", TEMP_CELSIUS, "mdi:thermometer"],
     "lastxfer": ["Last Transfer", "", "mdi:transfer"],
     "linefail": ["Input Voltage Status", "", "mdi:information-outline"],
     "linefreq": ["Line Frequency", "Hz", "mdi:information-outline"],
-    "linev": ["Input Voltage", "V", "mdi:flash"],
+    "linev": ["Input Voltage", UNIT_VOLT, "mdi:flash"],
     "loadpct": ["Load", UNIT_PERCENTAGE, "mdi:gauge"],
     "loadapnt": ["Load Apparent Power", UNIT_PERCENTAGE, "mdi:gauge"],
-    "lotrans": ["Transfer Low", "V", "mdi:flash"],
+    "lotrans": ["Transfer Low", UNIT_VOLT, "mdi:flash"],
     "mandate": ["Manufacture Date", "", "mdi:calendar"],
     "masterupd": ["Master Update", "", "mdi:information-outline"],
-    "maxlinev": ["Input Voltage High", "V", "mdi:flash"],
+    "maxlinev": ["Input Voltage High", UNIT_VOLT, "mdi:flash"],
     "maxtime": ["Battery Timeout", "", "mdi:timer-off"],
     "mbattchg": ["Battery Shutdown", UNIT_PERCENTAGE, "mdi:battery-alert"],
-    "minlinev": ["Input Voltage Low", "V", "mdi:flash"],
+    "minlinev": ["Input Voltage Low", UNIT_VOLT, "mdi:flash"],
     "mintimel": ["Shutdown Time", "", "mdi:timer"],
     "model": ["Model", "", "mdi:information-outline"],
-    "nombattv": ["Battery Nominal Voltage", "V", "mdi:flash"],
-    "nominv": ["Nominal Input Voltage", "V", "mdi:flash"],
-    "nomoutv": ["Nominal Output Voltage", "V", "mdi:flash"],
+    "nombattv": ["Battery Nominal Voltage", UNIT_VOLT, "mdi:flash"],
+    "nominv": ["Nominal Input Voltage", UNIT_VOLT, "mdi:flash"],
+    "nomoutv": ["Nominal Output Voltage", UNIT_VOLT, "mdi:flash"],
     "nompower": ["Nominal Output Power", POWER_WATT, "mdi:flash"],
     "nomapnt": ["Nominal Apparent Power", "VA", "mdi:flash"],
     "numxfers": ["Transfer Count", "", "mdi:counter"],
     "outcurnt": ["Output Current", "A", "mdi:flash"],
-    "outputv": ["Output Voltage", "V", "mdi:flash"],
+    "outputv": ["Output Voltage", UNIT_VOLT, "mdi:flash"],
     "reg1": ["Register 1 Fault", "", "mdi:information-outline"],
     "reg2": ["Register 2 Fault", "", "mdi:information-outline"],
     "reg3": ["Register 3 Fault", "", "mdi:information-outline"],
@@ -95,7 +96,7 @@ INFERRED_UNITS = {
     " Minutes": TIME_MINUTES,
     " Seconds": TIME_SECONDS,
     " Percent": UNIT_PERCENTAGE,
-    " Volts": "V",
+    " Volts": UNIT_VOLT,
     " Ampere": "A",
     " Volt-Ampere": "VA",
     " Watts": POWER_WATT,
diff --git a/homeassistant/components/dsmr_reader/definitions.py b/homeassistant/components/dsmr_reader/definitions.py
index 64eb2d9ea80..87e6d6ff872 100644
--- a/homeassistant/components/dsmr_reader/definitions.py
+++ b/homeassistant/components/dsmr_reader/definitions.py
@@ -1,6 +1,6 @@
 """Definitions for DSMR Reader sensors added to MQTT."""
 
-from homeassistant.const import ENERGY_KILO_WATT_HOUR, VOLUME_CUBIC_METERS
+from homeassistant.const import ENERGY_KILO_WATT_HOUR, UNIT_VOLT, VOLUME_CUBIC_METERS
 
 
 def dsmr_transform(value):
@@ -86,17 +86,17 @@ DEFINITIONS = {
     "dsmr/reading/phase_voltage_l1": {
         "name": "Current voltage L1",
         "icon": "mdi:flash",
-        "unit": "V",
+        "unit": UNIT_VOLT,
     },
     "dsmr/reading/phase_voltage_l2": {
         "name": "Current voltage L2",
         "icon": "mdi:flash",
-        "unit": "V",
+        "unit": UNIT_VOLT,
     },
     "dsmr/reading/phase_voltage_l3": {
         "name": "Current voltage L3",
         "icon": "mdi:flash",
-        "unit": "V",
+        "unit": UNIT_VOLT,
     },
     "dsmr/consumption/gas/delivered": {
         "name": "Gas usage",
diff --git a/homeassistant/components/elkm1/sensor.py b/homeassistant/components/elkm1/sensor.py
index 79987d806a1..0c7a454990d 100644
--- a/homeassistant/components/elkm1/sensor.py
+++ b/homeassistant/components/elkm1/sensor.py
@@ -7,6 +7,8 @@ from elkm1_lib.const import (
 )
 from elkm1_lib.util import pretty_const, username
 
+from homeassistant.const import UNIT_VOLT
+
 from . import ElkAttachedEntity, create_elk_entities
 from .const import DOMAIN
 
@@ -195,7 +197,7 @@ class ElkZone(ElkSensor):
         if self._element.definition == ZoneType.TEMPERATURE.value:
             return self._temperature_unit
         if self._element.definition == ZoneType.ANALOG_ZONE.value:
-            return "V"
+            return UNIT_VOLT
         return None
 
     def _element_changed(self, element, changeset):
diff --git a/homeassistant/components/envirophat/sensor.py b/homeassistant/components/envirophat/sensor.py
index ce1f154f911..81420cf389f 100644
--- a/homeassistant/components/envirophat/sensor.py
+++ b/homeassistant/components/envirophat/sensor.py
@@ -6,7 +6,7 @@ import logging
 import voluptuous as vol
 
 from homeassistant.components.sensor import PLATFORM_SCHEMA
-from homeassistant.const import CONF_DISPLAY_OPTIONS, CONF_NAME, TEMP_CELSIUS
+from homeassistant.const import CONF_DISPLAY_OPTIONS, CONF_NAME, TEMP_CELSIUS, UNIT_VOLT
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.entity import Entity
 from homeassistant.util import Throttle
@@ -31,10 +31,10 @@ SENSOR_TYPES = {
     "magnetometer_z": ["magnetometer_z", " ", "mdi:magnet"],
     "temperature": ["temperature", TEMP_CELSIUS, "mdi:thermometer"],
     "pressure": ["pressure", "hPa", "mdi:gauge"],
-    "voltage_0": ["voltage_0", "V", "mdi:flash"],
-    "voltage_1": ["voltage_1", "V", "mdi:flash"],
-    "voltage_2": ["voltage_2", "V", "mdi:flash"],
-    "voltage_3": ["voltage_3", "V", "mdi:flash"],
+    "voltage_0": ["voltage_0", UNIT_VOLT, "mdi:flash"],
+    "voltage_1": ["voltage_1", UNIT_VOLT, "mdi:flash"],
+    "voltage_2": ["voltage_2", UNIT_VOLT, "mdi:flash"],
+    "voltage_3": ["voltage_3", UNIT_VOLT, "mdi:flash"],
 }
 
 PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend(
diff --git a/homeassistant/components/greeneye_monitor/sensor.py b/homeassistant/components/greeneye_monitor/sensor.py
index ff5aff6fe50..18d564765d1 100644
--- a/homeassistant/components/greeneye_monitor/sensor.py
+++ b/homeassistant/components/greeneye_monitor/sensor.py
@@ -8,6 +8,7 @@ from homeassistant.const import (
     TIME_HOURS,
     TIME_MINUTES,
     TIME_SECONDS,
+    UNIT_VOLT,
 )
 from homeassistant.helpers.entity import Entity
 
@@ -310,4 +311,4 @@ class VoltageSensor(GEMSensor):
     @property
     def unit_of_measurement(self):
         """Return the unit of measurement for this sensor."""
-        return "V"
+        return UNIT_VOLT
diff --git a/homeassistant/components/growatt_server/sensor.py b/homeassistant/components/growatt_server/sensor.py
index b7cea620a66..6742b39e8b0 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,
+    UNIT_VOLT,
 )
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.entity import Entity
@@ -57,17 +58,17 @@ INVERTER_SENSOR_TYPES = {
         "e_total",
         "power",
     ),
-    "inverter_voltage_input_1": ("Input 1 voltage", "V", "vpv1", None),
+    "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_voltage_input_2": ("Input 2 voltage", "V", "vpv2", None),
+    "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_voltage_input_3": ("Input 3 voltage", "V", "vpv3", None),
+    "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_reactive_voltage": ("Reactive voltage", "V", "vacr", None),
+    "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"),
diff --git a/homeassistant/components/homematic/sensor.py b/homeassistant/components/homematic/sensor.py
index c0a269bd582..d36b05fd129 100644
--- a/homeassistant/components/homematic/sensor.py
+++ b/homeassistant/components/homematic/sensor.py
@@ -11,6 +11,7 @@ from homeassistant.const import (
     SPEED_KILOMETERS_PER_HOUR,
     TEMP_CELSIUS,
     UNIT_PERCENTAGE,
+    UNIT_VOLT,
     VOLUME_CUBIC_METERS,
 )
 
@@ -40,7 +41,7 @@ HM_UNIT_HA_CAST = {
     "BRIGHTNESS": "#",
     "POWER": POWER_WATT,
     "CURRENT": "mA",
-    "VOLTAGE": "V",
+    "VOLTAGE": UNIT_VOLT,
     "ENERGY_COUNTER": ENERGY_WATT_HOUR,
     "GAS_POWER": VOLUME_CUBIC_METERS,
     "GAS_ENERGY_COUNTER": VOLUME_CUBIC_METERS,
diff --git a/homeassistant/components/isy994/sensor.py b/homeassistant/components/isy994/sensor.py
index 9e2f3e90957..a21b484ec9b 100644
--- a/homeassistant/components/isy994/sensor.py
+++ b/homeassistant/components/isy994/sensor.py
@@ -20,6 +20,7 @@ from homeassistant.const import (
     TIME_YEARS,
     UNIT_PERCENTAGE,
     UNIT_UV_INDEX,
+    UNIT_VOLT,
 )
 from homeassistant.helpers.typing import ConfigType
 
@@ -91,7 +92,7 @@ UOM_FRIENDLY_NAME = {
     "65": "SML",
     "69": "gal",
     "71": UNIT_UV_INDEX,
-    "72": "V",
+    "72": UNIT_VOLT,
     "73": POWER_WATT,
     "74": "W/m²",
     "75": "weekday",
diff --git a/homeassistant/components/juicenet/sensor.py b/homeassistant/components/juicenet/sensor.py
index 6ddb8279811..93eec19d41b 100644
--- a/homeassistant/components/juicenet/sensor.py
+++ b/homeassistant/components/juicenet/sensor.py
@@ -1,7 +1,13 @@
 """Support for monitoring juicenet/juicepoint/juicebox based EVSE sensors."""
 import logging
 
-from homeassistant.const import ENERGY_WATT_HOUR, POWER_WATT, TEMP_CELSIUS, TIME_SECONDS
+from homeassistant.const import (
+    ENERGY_WATT_HOUR,
+    POWER_WATT,
+    TEMP_CELSIUS,
+    TIME_SECONDS,
+    UNIT_VOLT,
+)
 from homeassistant.helpers.entity import Entity
 
 from . import DOMAIN, JuicenetDevice
@@ -11,7 +17,7 @@ _LOGGER = logging.getLogger(__name__)
 SENSOR_TYPES = {
     "status": ["Charging Status", None],
     "temperature": ["Temperature", TEMP_CELSIUS],
-    "voltage": ["Voltage", "V"],
+    "voltage": ["Voltage", UNIT_VOLT],
     "amps": ["Amps", "A"],
     "watts": ["Watts", POWER_WATT],
     "charge_time": ["Charge time", TIME_SECONDS],
diff --git a/homeassistant/components/lcn/const.py b/homeassistant/components/lcn/const.py
index 0a46190fbf9..7a881ab9d85 100644
--- a/homeassistant/components/lcn/const.py
+++ b/homeassistant/components/lcn/const.py
@@ -1,7 +1,12 @@
 """Constants for the LCN component."""
 from itertools import product
 
-from homeassistant.const import TEMP_CELSIUS, TEMP_FAHRENHEIT, UNIT_PERCENTAGE
+from homeassistant.const import (
+    TEMP_CELSIUS,
+    TEMP_FAHRENHEIT,
+    UNIT_PERCENTAGE,
+    UNIT_VOLT,
+)
 
 DOMAIN = "lcn"
 DATA_LCN = "lcn"
@@ -157,7 +162,7 @@ VAR_UNITS = [
     "PERCENT",
     "PPM",
     "VOLT",
-    "V",
+    UNIT_VOLT,
     "AMPERE",
     "AMP",
     "A",
diff --git a/homeassistant/components/mysensors/sensor.py b/homeassistant/components/mysensors/sensor.py
index 997728ed495..16c8d37f447 100644
--- a/homeassistant/components/mysensors/sensor.py
+++ b/homeassistant/components/mysensors/sensor.py
@@ -8,6 +8,7 @@ from homeassistant.const import (
     TEMP_CELSIUS,
     TEMP_FAHRENHEIT,
     UNIT_PERCENTAGE,
+    UNIT_VOLT,
 )
 
 SENSORS = {
@@ -35,7 +36,7 @@ SENSORS = {
         "S_VIBRATION": ["Hz", None],
         "S_LIGHT_LEVEL": ["lx", "mdi:white-balance-sunny"],
     },
-    "V_VOLTAGE": ["V", "mdi:flash"],
+    "V_VOLTAGE": [UNIT_VOLT, "mdi:flash"],
     "V_CURRENT": ["A", "mdi:flash-auto"],
     "V_PH": ["pH", None],
     "V_ORP": ["mV", None],
diff --git a/homeassistant/components/nut/const.py b/homeassistant/components/nut/const.py
index 98b6d22a830..50217e4b598 100644
--- a/homeassistant/components/nut/const.py
+++ b/homeassistant/components/nut/const.py
@@ -4,7 +4,13 @@ from homeassistant.components.sensor import (
     DEVICE_CLASS_POWER,
     DEVICE_CLASS_TEMPERATURE,
 )
-from homeassistant.const import POWER_WATT, TEMP_CELSIUS, TIME_SECONDS, UNIT_PERCENTAGE
+from homeassistant.const import (
+    POWER_WATT,
+    TEMP_CELSIUS,
+    TIME_SECONDS,
+    UNIT_PERCENTAGE,
+    UNIT_VOLT,
+)
 
 DOMAIN = "nut"
 
@@ -94,10 +100,15 @@ SENSOR_TYPES = {
         None,
     ],
     "battery.charger.status": ["Charging Status", "", "mdi:information-outline", None],
-    "battery.voltage": ["Battery Voltage", "V", "mdi:flash", None],
-    "battery.voltage.nominal": ["Nominal Battery Voltage", "V", "mdi:flash", None],
-    "battery.voltage.low": ["Low Battery Voltage", "V", "mdi:flash", None],
-    "battery.voltage.high": ["High Battery Voltage", "V", "mdi:flash", None],
+    "battery.voltage": ["Battery Voltage", UNIT_VOLT, "mdi:flash", None],
+    "battery.voltage.nominal": [
+        "Nominal Battery Voltage",
+        UNIT_VOLT,
+        "mdi:flash",
+        None,
+    ],
+    "battery.voltage.low": ["Low Battery Voltage", UNIT_VOLT, "mdi:flash", None],
+    "battery.voltage.high": ["High Battery Voltage", UNIT_VOLT, "mdi:flash", None],
     "battery.capacity": ["Battery Capacity", "Ah", "mdi:flash", None],
     "battery.current": ["Battery Current", "A", "mdi:flash", None],
     "battery.current.total": ["Total Battery Current", "A", "mdi:flash", None],
@@ -137,16 +148,16 @@ SENSOR_TYPES = {
         "mdi:information-outline",
         None,
     ],
-    "input.transfer.low": ["Low Voltage Transfer", "V", "mdi:flash", None],
-    "input.transfer.high": ["High Voltage Transfer", "V", "mdi:flash", None],
+    "input.transfer.low": ["Low Voltage Transfer", UNIT_VOLT, "mdi:flash", None],
+    "input.transfer.high": ["High Voltage Transfer", UNIT_VOLT, "mdi:flash", None],
     "input.transfer.reason": [
         "Voltage Transfer Reason",
         "",
         "mdi:information-outline",
         None,
     ],
-    "input.voltage": ["Input Voltage", "V", "mdi:flash", None],
-    "input.voltage.nominal": ["Nominal Input Voltage", "V", "mdi:flash", None],
+    "input.voltage": ["Input Voltage", UNIT_VOLT, "mdi:flash", None],
+    "input.voltage.nominal": ["Nominal Input Voltage", UNIT_VOLT, "mdi:flash", None],
     "input.frequency": ["Input Line Frequency", "hz", "mdi:flash", None],
     "input.frequency.nominal": [
         "Nominal Input Line Frequency",
@@ -162,8 +173,8 @@ SENSOR_TYPES = {
     ],
     "output.current": ["Output Current", "A", "mdi:flash", None],
     "output.current.nominal": ["Nominal Output Current", "A", "mdi:flash", None],
-    "output.voltage": ["Output Voltage", "V", "mdi:flash", None],
-    "output.voltage.nominal": ["Nominal Output Voltage", "V", "mdi:flash", None],
+    "output.voltage": ["Output Voltage", UNIT_VOLT, "mdi:flash", None],
+    "output.voltage.nominal": ["Nominal Output Voltage", UNIT_VOLT, "mdi:flash", None],
     "output.frequency": ["Output Frequency", "hz", "mdi:flash", None],
     "output.frequency.nominal": ["Nominal Output Frequency", "hz", "mdi:flash", None],
 }
diff --git a/homeassistant/components/onewire/sensor.py b/homeassistant/components/onewire/sensor.py
index 90d943dd755..d38c115c9d4 100644
--- a/homeassistant/components/onewire/sensor.py
+++ b/homeassistant/components/onewire/sensor.py
@@ -8,7 +8,13 @@ from pyownet import protocol
 import voluptuous as vol
 
 from homeassistant.components.sensor import PLATFORM_SCHEMA
-from homeassistant.const import CONF_HOST, CONF_PORT, TEMP_CELSIUS, UNIT_PERCENTAGE
+from homeassistant.const import (
+    CONF_HOST,
+    CONF_PORT,
+    TEMP_CELSIUS,
+    UNIT_PERCENTAGE,
+    UNIT_VOLT,
+)
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.entity import Entity
 
@@ -75,9 +81,9 @@ SENSOR_TYPES = {
     "counter_a": ["counter", "count"],
     "counter_b": ["counter", "count"],
     "HobbyBoard": ["none", "none"],
-    "voltage": ["voltage", "V"],
-    "voltage_VAD": ["voltage", "V"],
-    "voltage_VDD": ["voltage", "V"],
+    "voltage": ["voltage", UNIT_VOLT],
+    "voltage_VAD": ["voltage", UNIT_VOLT],
+    "voltage_VDD": ["voltage", UNIT_VOLT],
     "current": ["current", "A"],
 }
 
diff --git a/homeassistant/components/smappee/sensor.py b/homeassistant/components/smappee/sensor.py
index 8f1e034dcac..5948f7e4223 100644
--- a/homeassistant/components/smappee/sensor.py
+++ b/homeassistant/components/smappee/sensor.py
@@ -6,6 +6,7 @@ from homeassistant.const import (
     ENERGY_KILO_WATT_HOUR,
     POWER_WATT,
     UNIT_PERCENTAGE,
+    UNIT_VOLT,
     VOLUME_CUBIC_METERS,
 )
 from homeassistant.helpers.entity import Entity
@@ -25,7 +26,7 @@ SENSOR_TYPES = {
         "active_power",
     ],
     "current": ["Current", "mdi:gauge", "local", "A", "current"],
-    "voltage": ["Voltage", "mdi:gauge", "local", "V", "voltage"],
+    "voltage": ["Voltage", "mdi:gauge", "local", UNIT_VOLT, "voltage"],
     "active_cosfi": [
         "Power Factor",
         "mdi:gauge",
diff --git a/homeassistant/components/smartthings/sensor.py b/homeassistant/components/smartthings/sensor.py
index 630fbaadd3a..da581bb969e 100644
--- a/homeassistant/components/smartthings/sensor.py
+++ b/homeassistant/components/smartthings/sensor.py
@@ -17,6 +17,7 @@ from homeassistant.const import (
     TEMP_CELSIUS,
     TEMP_FAHRENHEIT,
     UNIT_PERCENTAGE,
+    UNIT_VOLT,
 )
 
 from . import SmartThingsEntity
@@ -233,7 +234,7 @@ CAPABILITY_TO_SENSORS = {
         Map(Attribute.ultraviolet_index, "Ultraviolet Index", None, None)
     ],
     Capability.voltage_measurement: [
-        Map(Attribute.voltage, "Voltage Measurement", "V", None)
+        Map(Attribute.voltage, "Voltage Measurement", UNIT_VOLT, None)
     ],
     Capability.washer_mode: [Map(Attribute.washer_mode, "Washer Mode", None, None)],
     Capability.washer_operating_state: [
diff --git a/homeassistant/components/solaredge_local/sensor.py b/homeassistant/components/solaredge_local/sensor.py
index ecf9dfde8b1..8d1b7262fc0 100644
--- a/homeassistant/components/solaredge_local/sensor.py
+++ b/homeassistant/components/solaredge_local/sensor.py
@@ -16,6 +16,7 @@ from homeassistant.const import (
     POWER_WATT,
     TEMP_CELSIUS,
     TEMP_FAHRENHEIT,
+    UNIT_VOLT,
 )
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.entity import Entity
@@ -40,8 +41,20 @@ INVERTER_MODES = (
 # Supported sensor types:
 # Key: ['json_key', 'name', unit, icon, attribute name]
 SENSOR_TYPES = {
-    "current_AC_voltage": ["gridvoltage", "Grid Voltage", "V", "mdi:current-ac", None],
-    "current_DC_voltage": ["dcvoltage", "DC Voltage", "V", "mdi:current-dc", None],
+    "current_AC_voltage": [
+        "gridvoltage",
+        "Grid Voltage",
+        UNIT_VOLT,
+        "mdi:current-ac",
+        None,
+    ],
+    "current_DC_voltage": [
+        "dcvoltage",
+        "DC Voltage",
+        UNIT_VOLT,
+        "mdi:current-dc",
+        None,
+    ],
     "current_frequency": [
         "gridfrequency",
         "Grid Frequency",
@@ -122,7 +135,7 @@ SENSOR_TYPES = {
     "optimizer_voltage": [
         "optimizervoltage",
         "Average Optimizer Voltage",
-        "V",
+        UNIT_VOLT,
         "mdi:solar-panel",
         None,
     ],
diff --git a/homeassistant/components/solarlog/const.py b/homeassistant/components/solarlog/const.py
index 26176e97e46..b8512531f36 100644
--- a/homeassistant/components/solarlog/const.py
+++ b/homeassistant/components/solarlog/const.py
@@ -1,7 +1,12 @@
 """Constants for the Solar-Log integration."""
 from datetime import timedelta
 
-from homeassistant.const import ENERGY_KILO_WATT_HOUR, POWER_WATT, UNIT_PERCENTAGE
+from homeassistant.const import (
+    ENERGY_KILO_WATT_HOUR,
+    POWER_WATT,
+    UNIT_PERCENTAGE,
+    UNIT_VOLT,
+)
 
 DOMAIN = "solarlog"
 
@@ -17,8 +22,8 @@ SENSOR_TYPES = {
     "time": ["TIME", "last update", None, "mdi:calendar-clock"],
     "power_ac": ["powerAC", "power AC", POWER_WATT, "mdi:solar-power"],
     "power_dc": ["powerDC", "power DC", POWER_WATT, "mdi:solar-power"],
-    "voltage_ac": ["voltageAC", "voltage AC", "V", "mdi:flash"],
-    "voltage_dc": ["voltageDC", "voltage DC", "V", "mdi:flash"],
+    "voltage_ac": ["voltageAC", "voltage AC", UNIT_VOLT, "mdi:flash"],
+    "voltage_dc": ["voltageDC", "voltage DC", UNIT_VOLT, "mdi:flash"],
     "yield_day": ["yieldDAY", "yield day", ENERGY_KILO_WATT_HOUR, "mdi:solar-power"],
     "yield_yesterday": [
         "yieldYESTERDAY",
diff --git a/homeassistant/components/starline/sensor.py b/homeassistant/components/starline/sensor.py
index 8e17caad86c..09642e66479 100644
--- a/homeassistant/components/starline/sensor.py
+++ b/homeassistant/components/starline/sensor.py
@@ -1,6 +1,6 @@
 """Reads vehicle status from StarLine API."""
 from homeassistant.components.sensor import DEVICE_CLASS_TEMPERATURE
-from homeassistant.const import TEMP_CELSIUS, UNIT_PERCENTAGE
+from homeassistant.const import TEMP_CELSIUS, UNIT_PERCENTAGE, UNIT_VOLT
 from homeassistant.helpers.entity import Entity
 from homeassistant.helpers.icon import icon_for_battery_level, icon_for_signal_level
 
@@ -9,7 +9,7 @@ from .const import DOMAIN
 from .entity import StarlineEntity
 
 SENSOR_TYPES = {
-    "battery": ["Battery", None, "V", None],
+    "battery": ["Battery", None, UNIT_VOLT, None],
     "balance": ["Balance", None, None, "mdi:cash-multiple"],
     "ctemp": ["Interior Temperature", DEVICE_CLASS_TEMPERATURE, TEMP_CELSIUS, None],
     "etemp": ["Engine Temperature", DEVICE_CLASS_TEMPERATURE, TEMP_CELSIUS, None],
diff --git a/homeassistant/components/ted5000/sensor.py b/homeassistant/components/ted5000/sensor.py
index 2e6246d06dd..3982c7f0d04 100644
--- a/homeassistant/components/ted5000/sensor.py
+++ b/homeassistant/components/ted5000/sensor.py
@@ -7,7 +7,7 @@ import voluptuous as vol
 import xmltodict
 
 from homeassistant.components.sensor import PLATFORM_SCHEMA
-from homeassistant.const import CONF_HOST, CONF_NAME, CONF_PORT, POWER_WATT
+from homeassistant.const import CONF_HOST, CONF_NAME, CONF_PORT, POWER_WATT, UNIT_VOLT
 from homeassistant.helpers import config_validation as cv
 from homeassistant.helpers.entity import Entity
 from homeassistant.util import Throttle
@@ -43,7 +43,7 @@ def setup_platform(hass, config, add_entities, discovery_info=None):
     dev = []
     for mtu in gateway.data:
         dev.append(Ted5000Sensor(gateway, name, mtu, POWER_WATT))
-        dev.append(Ted5000Sensor(gateway, name, mtu, "V"))
+        dev.append(Ted5000Sensor(gateway, name, mtu, UNIT_VOLT))
 
     add_entities(dev)
     return True
@@ -54,7 +54,7 @@ class Ted5000Sensor(Entity):
 
     def __init__(self, gateway, name, mtu, unit):
         """Initialize the sensor."""
-        units = {POWER_WATT: "power", "V": "voltage"}
+        units = {POWER_WATT: "power", UNIT_VOLT: "voltage"}
         self._gateway = gateway
         self._name = "{} mtu{} {}".format(name, mtu, units[unit])
         self._mtu = mtu
@@ -108,4 +108,4 @@ class Ted5000Gateway:
                 power = int(doc["LiveData"]["Power"]["MTU%d" % mtu]["PowerNow"])
                 voltage = int(doc["LiveData"]["Voltage"]["MTU%d" % mtu]["VoltageNow"])
 
-                self.data[mtu] = {POWER_WATT: power, "V": voltage / 10}
+                self.data[mtu] = {POWER_WATT: power, UNIT_VOLT: voltage / 10}
diff --git a/homeassistant/components/wirelesstag/__init__.py b/homeassistant/components/wirelesstag/__init__.py
index 7296179a126..335b24b8557 100644
--- a/homeassistant/components/wirelesstag/__init__.py
+++ b/homeassistant/components/wirelesstag/__init__.py
@@ -12,6 +12,7 @@ from homeassistant.const import (
     CONF_PASSWORD,
     CONF_USERNAME,
     UNIT_PERCENTAGE,
+    UNIT_VOLT,
 )
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.dispatcher import dispatcher_send
@@ -280,7 +281,7 @@ class WirelessTagBaseSensor(Entity):
         """Return the state attributes."""
         return {
             ATTR_BATTERY_LEVEL: int(self._tag.battery_remaining * 100),
-            ATTR_VOLTAGE: f"{self._tag.battery_volts:.2f}V",
+            ATTR_VOLTAGE: f"{self._tag.battery_volts:.2f}{UNIT_VOLT}",
             ATTR_TAG_SIGNAL_STRENGTH: f"{self._tag.signal_strength}dBm",
             ATTR_TAG_OUT_OF_RANGE: not self._tag.is_in_range,
             ATTR_TAG_POWER_CONSUMPTION: f"{self._tag.power_consumption:.2f}{UNIT_PERCENTAGE}",
diff --git a/homeassistant/const.py b/homeassistant/const.py
index 42b944e9fb3..d69f0370720 100644
--- a/homeassistant/const.py
+++ b/homeassistant/const.py
@@ -345,6 +345,9 @@ ATTR_TEMPERATURE = "temperature"
 # Power units
 POWER_WATT = "W"
 
+# Voltage units
+UNIT_VOLT = "V"
+
 # Energy units
 ENERGY_KILO_WATT_HOUR = "kWh"
 ENERGY_WATT_HOUR = "Wh"
diff --git a/tests/components/sma/test_sensor.py b/tests/components/sma/test_sensor.py
index 3caf889c522..2556a0d2e76 100644
--- a/tests/components/sma/test_sensor.py
+++ b/tests/components/sma/test_sensor.py
@@ -2,6 +2,7 @@
 import logging
 
 from homeassistant.components.sensor import DOMAIN
+from homeassistant.const import UNIT_VOLT
 from homeassistant.setup import async_setup_component
 
 from tests.common import assert_setup_component
@@ -11,7 +12,7 @@ BASE_CFG = {
     "platform": "sma",
     "host": "1.1.1.1",
     "password": "",
-    "custom": {"my_sensor": {"key": "1234567890123", "unit": "V"}},
+    "custom": {"my_sensor": {"key": "1234567890123", "unit": UNIT_VOLT}},
 }