Sensor

Sensors are a basic integration in Home Assistant. They monitor the states and conditions of a variety of entities. An entity can be many things. This can include a physical device like a motion sensor that reports the battery level, a web service that retrieves the weather temperature, a built-in function that calculates the sun’s elevation relative to your GPS position, or even a custom sensor you may have created to report the free space on your laptop. These are all things reporting different types of information.

Some of these sensors are built-in to Home Assistant, some are created automatically when you add an integration (see this list), and some can be created manually. The Statistics and Template sensors are two examples of the last case.

The state of a sensor entity

The state of a sensor entity is its currently detected value, which can be either text or a number.

Screenshot showing the state of a sensor entity in the developer tools.

In addition, the entity can have the following states:

• Unavailable: The entity is currently unavailable.
• Unknown: The state is not yet known.

Device class

A device class is a measurement categorization in Home Assistant. It influences how the entity is represented in the dashboard. This can be modified in the customize section. For example, different states may be represented by different icons, colors, or text.

The screenshot shows different icons representing different device classes for sensors:

Example of various device class icons for sensors.

The following device classes are supported for sensors:

• None: Generic sensor. This is the default and doesn’t need to be set.
• apparent_power: Apparent power in VA.
• aqi: Air Quality Index (unitless).
• atmospheric_pressure: Atmospheric pressure in cbar, bar, hPa, mmHg, inHg, kPa, mbar, Pa or psi
• battery: Percentage of battery that is left in %
• carbon_dioxide: Carbon Dioxide in CO2 (Smoke) in ppm
• carbon_monoxide: Carbon Monoxide in CO (Gas CNG/LPG) in ppm
• current: Current in A, mA
• data_rate: Data rate in bit/s, kbit/s, Mbit/s, Gbit/s, B/s, kB/s, MB/s, GB/s, KiB/s, MiB/s or GiB/s
• data_size: Data size in bit, kbit, Mbit, Gbit, B, kB, MB, GB, TB, PB, EB, ZB, YB, KiB, MiB, GiB, TiB, PiB, EiB, ZiB or YiB
• date: Date string (ISO 8601)
• distance: Generic distance in km, m, cm, mm, mi, nmi, yd, or in
• duration: Duration in d, h, min, s, or ms
• energy: Energy in J, kJ, MJ, GJ, Wh, kWh, MWh, cal, kcal, Mcal, or Gcal
• energy_storage: Stored energy in J, kJ, MJ, GJ, Wh, kWh, MWh, cal, kcal, Mcal, or Gcal
• enum: Has a limited set of (non-numeric) states
• frequency: Frequency in Hz, kHz, MHz, or GHz
• gas: Gasvolume in m³, ft³ or CCF
• humidity: Percentage of humidity in the air in %
• illuminance: The current light level in lx
• irradiance: Irradiance in W/m² or BTU/(h⋅ft²)
• moisture: Percentage of water in a substance in %
• monetary: The monetary value (ISO 4217)
• nitrogen_dioxide: Concentration of Nitrogen Dioxide in µg/m³
• nitrogen_monoxide: Concentration of Nitrogen Monoxide in µg/m³
• nitrous_oxide: Concentration of Nitrous Oxide in µg/m³
• ozone: Concentration of Ozone in µg/m³
• ph: Potential hydrogen (pH) value of a water solution
• pm1: Concentration of particulate matter less than 1 micrometer in µg/m³
• pm25: Concentration of particulate matter less than 2.5 micrometers in µg/m³
• pm10: Concentration of particulate matter less than 10 micrometers in µg/m³
• power_factor: Power factor (unitless), unit may be None or %
• power: Power in W or kW
• precipitation: Accumulated precipitation in cm, in or mm
• precipitation_intensity: Precipitation intensity in in/d, in/h, mm/d or mm/h
• pressure: Pressure in Pa, kPa, hPa, bar, cbar, mbar, mmHg, inHg or psi
• reactive_power: Reactive power in var
• signal_strength: Signal strength in dB or dBm
• sound_pressure: Sound pressure in dB or dBA
• speed: Generic speed in ft/s, in/d, in/h, in/s, km/h, kn, m/s, mph, mm/d, or mm/s
• sulphur_dioxide: Concentration of sulphur dioxide in µg/m³
• temperature: Temperature in °C, °F or K
• timestamp: Datetime object or timestamp string (ISO 8601)
• volatile_organic_compounds: Concentration of volatile organic compounds in µg/m³
• volatile_organic_compounds_parts: Ratio of volatile organic compounds in ppm or ppb
• voltage: Voltage in V, mV
• volume: Generic volume in L, mL, gal, fl. oz., m³, ft³, or CCF
• volume_flow_rate: Volume flow rate in m³/h, ft³/min, L/min, gal/min
• volume_storage: Generic stored volume in L, mL, gal, fl. oz., m³, ft³, or CCF
• water: Water consumption in L, gal, m³, ft³, or CCF
• weight: Generic mass in kg, g, mg, µg, oz, lb, or st
• wind_speed: Wind speed in Beaufort, ft/s, km/h, kn, m/s, or mph