Room-by-room temperature sensors and heating automations in Home Assistant

The thermostat says the house is warm. Your cold room would like a word. A few well-placed temperature sensors let you see what each room is doing, spot the outlier and stop adjusting the whole heating system by guesswork.

Start with SONOFF SNZB-02D if you want a screen, or the Aqara Temperature and Humidity three-pack if you want small sensors in several rooms. Choose Aqara W100 for an existing Matter-over-Thread setup, Zooz ZSE44 800LR for Z-Wave, and SONOFF SNZB-02P for a screen-free Zigbee two-pack.

This research-based guide uses the makers’ specifications and Home Assistant and Zigbee2MQTT documentation.

Pick the sensor that fits your radio—and your eyes

Your priority	Pick	Why it fits
Best display sensor	SONOFF SNZB-02D	Read temperature and humidity without opening an app
Best tiny sensor	Aqara Temperature and Humidity Sensor	Small 36 × 36 × 9 mm body; the selected pack contains three sensors
Best Thread option	Aqara Climate Sensor W100	Matter over Thread, with Zigbee as an alternative mode
Best Z-Wave option	Zooz ZSE44 800LR	Adds readings to your existing Z-Wave network
Screen-free room pair	SONOFF SNZB-02P	Two sensors in the selected pack, with a replaceable CR2477 battery in each

You are choosing alternatives, not a shopping challenge to collect all five. Start with the room that feels wrong and a second room for comparison. Already have the Aqara sensors from the Home Assistant starter kit? Put them to work before adding another radio.

What you are actually buying

Sensor / selected pack	Radio	Documented HA path	Useful detail
SONOFF SNZB-02D / one	Zigbee 3.0	Zigbee2MQTT	LCD and CR2450 battery
Aqara original WSDCGQ11LM / three	Zigbee	Zigbee2MQTT; starter-kit ZHA setup	CR2032 battery; small, screen-free body
SONOFF SNZB-02P / two	Zigbee 3.0	Zigbee2MQTT	Screen-free; CR2477 battery
Aqara W100 / one	Thread or Zigbee	HA Matter over Thread, or Zigbee2MQTT in Zigbee mode	Choose the protocol before pairing
Zooz ZSE44 800LR / one	Z-Wave / Long Range	Z-Wave JS	CR2450 battery; current listing is the 800LR version

The maker references are SONOFF’s 02D manual, 02P manual, Aqara’s original sensor specification, W100 specification and Zooz’s 800LR manual. Use the exact model’s route rather than assuming every sensor with the same brand name pairs the same way.

For the Zigbee2MQTT route, the project documents SNZB-02D, SNZB-02P and Aqara WSDCGQ11LM individually. Each exposes temperature and humidity. Our Zigbee coordinator guide helps with the radio choice.

W100: choose Thread or Zigbee

Pick W100 when you already have a Thread border router and want a Matter sensor on that network. Home Assistant needs its Matter integration as well as the Thread network and border router. A Zigbee coordinator alone does not supply that Thread route.

For Zigbee2MQTT, the W100 device page explains switching its shipping Thread firmware to Zigbee through the Aqara Home app, including the account step. Switch first, then pair it to your Zigbee coordinator. The two protocols are alternatives; you are not putting the same sensor on both networks at once.

Treat W100 as a room sensor for this project. Its extra HVAC and button features depend on the chosen integration and equipment; buying it does not turn an ordinary radiator into a remotely controlled valve.

For a W100 in Thread mode, follow our Matter-over-Thread setup guide to choose a border router, sync the phone credentials and commission it into Home Assistant.

Z-Wave already installed? Stay with it

ZSE44 is the neat choice when your Connect ZWA-2 network is already running. The current selected listing is ZSE44 800LR, so use the current manual rather than older 700-series instructions. Its maker lists an operating range of 40–90°F: this is a room-monitoring choice, not a freezer probe.

Use Z-Wave JS and the manual’s SmartStart sequence. Scan the QR code before powering the sensor when following that route, finish its interview, then inspect its temperature and humidity entities.

Already own a supported Bluetooth thermometer instead? An ESPHome Bluetooth proxy can bring its BLE readings into range. The Zigbee, Thread and Z-Wave picks here use their own radios.

Give every room a fair reading

Place sensors where you want to understand the air you spend time in. Avoid direct sun, a radiator’s hot plume, an open window’s draft and heat from electronics. A sensor tucked behind a warm computer will mostly tell you about the computer.

Before separating them, place the sensors together and let their readings settle. Investigate a conspicuous disagreement or a bad location. Then move them to their rooms and keep their positions consistent while you compare days.

Keep the indoor sensors away from splashes and condensation. In a bathroom, use a dry location that still reflects the room’s air, not the shower spray. SONOFF’s manuals specify non-condensing conditions.

Give each device an area and a readable name in Home Assistant. Pair one, identify its temperature and humidity entities, and watch both update before repeating the process. Keep temperature comparisons in the same unit. Battery percentages are useful for maintenance; the room temperature is the number you want on the main dashboard.

Graph every room on one screen

Open History in the sidebar. Under Sources, choose Add target, then select the temperature entities you want to compare. On a phone, open Sources from the toolbar. Choose the same time period for all rooms and look for the coldest overnight stretch or the room that warms last.

Once the view is useful, choose Menu → Add current view as card, then select your dashboard and view. These are the current History panel instructions; the History graph card documents its configuration.

Keep humidity on a separate graph so a percentage and a temperature do not compete for your attention. Start with a normal day of readings, then compare a similar day after one change. You will learn more from a clear before-and-after graph than from changing every radiator setting at once.

Heating: give your existing thermostat better clues

A room sensor measures; your thermostat or heating controls do the heating. Use the graph to decide whether the cold room needs attention, then adjust your existing controls. If you already have a supported thermostat or smart radiator valve connected to Home Assistant, build on that device’s documented control options.

The recipes below start with notifications rather than wiring a heater to a smart plug. Keep space heaters directly in a wall outlet, not a smart plug, following CPSC’s heater guidance. You do not need a new thermostat to get useful room graphs and a cold-room nudge.

For a sunny room, use the reading to close compatible blinds or curtains: our motorised window-covering guide shows the local-control hardware and a hot-room automation.

Three projects to build with the readings

Open Settings → Automations & scenes → Create automation → Create new automation for the first two recipes. Add triggers under When, conditions under And if, actions under Then do, and press Save before testing. Temperature, humidity and timing settings below are example preferences for you to tune.

1. A cold-room alert that catches an already-cold room

Use a Time trigger at your chosen morning check time. Add a Numeric state condition for that room’s temperature, Below: 18 if the entity uses Celsius, or Below: 64.4 if it uses Fahrenheit. Add your phone’s Companion notification action: “The room is below your chosen temperature—take a look at the heating setting.”

This checks the reading at the chosen time, so it still notices a room that became cold hours earlier. It does not depend on a fresh threshold crossing. The threshold is a comfort example, not a heating target you must adopt.

Follow the Time trigger, Numeric state condition and Companion notification guide. Numeric conditions exclude the boundary itself and fail for unknown or unavailable readings. Test with a temporary time a few minutes ahead, then restore the time you want and Save again.

2. Let humidity run a suitable plug-in bathroom fan

Use an existing plug-in fan whose instructions allow remote switching and a smart plug suitable for its motor load, placed outside wet and splash zones. Shelly Plug US Gen4 lists fans among its supported inductive loads; its headline 1,800 W limit is for resistive loads, so use the motor’s requirements rather than that number. A hardwired extractor needs its proper installed control, not an improvised plug adapter. See Shelly’s load specifications and our local-control smart-plug guide.

Create one automation with a Time pattern trigger, Minutes: /5. Under Then do, add Choose with two options:

• Humidity above 65% and the fan plug is off: run Switch: Turn on for that plug.
• Humidity below 60% and the fan plug is on: run Switch: Turn off for that plug.

Use Numeric state conditions for humidity and State conditions for the actual plug entity. Leave the default branch empty. Between the thresholds, at either exact boundary, or with missing humidity data, the automation leaves the plug as it is.

The Time pattern documentation explains /5; the Choose action selects a matching branch. Checking the current reading every five minutes catches a room that is already humid when you enable or restart the automation. It also avoids a collection of pending threshold timers. These thresholds are starting examples, not a ventilation standard.

Test both branches by temporarily setting a threshold on the appropriate side of the real reading. Restore 65/60—or your chosen values—and Save. Watch a real humidity rise and fall before leaving the routine in charge. If you also use mmWave presence for the fan, make one combined control routine rather than letting two automations fight over the switch.

3. A weekly temperature report card

Give each room a Statistic card showing the mean for the previous calendar week. Add a card to your dashboard, open its code editor and adapt this configuration with your own temperature entity:

type: statistic
entity: sensor.room_temperature
name: Last week — average temperature
stat_type: mean
period:
  calendar:
    period: week
    offset: -1

Duplicate it for each room. Make another copy with stat_type: min and a matching name if you want the lowest recorded temperature alongside the average. The Statistic card documentation defines mean, min, calendar week and offset: -1. This is the last calendar week, not a rolling seven-day average.

Home Assistant needs statistics for those entities. Its long-term statistics guide explains eligible sensor state classes and recorder exclusions. If a card has no data, look in Settings → Tools → Statistics and make sure the sensor is recording usable measurements. A new installation needs time to build a real history; the card cannot fill last week with readings it never received.

Now your weekly review has a job: find the consistently cold room, make one change to your existing heating controls, and compare the next week’s graph and cards. Let the graphs show whether the change helped.

Add air readings alongside the temperature graph with our Home Assistant air-quality guide. It separates CO₂ ventilation reminders, cooking particles and radon, with a previous-week report card.

Start with the cold room, not a whole-house shopping spree

Choose SNZB-02D for a visible readout, Aqara’s three-pack for tiny room sensors, W100 for Thread, or ZSE44 for Z-Wave. The 02P two-pack fits when you want Zigbee readings and will use your dashboard instead of a screen.

Get the first sensor reporting, add a second room for context, and build the cold-room alert. Then add humidity switching or the weekly report card. Return to the Home Assistant hub for more projects, or use the starter kit to build the host-and-radio foundation first.

Ready to connect the room readings to your heating plan? Our local-control thermostat guide compares Z-Wave, Matter and HomeKit routes, then builds an away setback and a cold-room comfort nudge.

Want the warm-room reading to do something useful? Our RM4 Mini vs Pro guide shows a learned AC cooling preset and a temperature-crossing automation.

Want to see what the weather is doing outside, too? Add an Ecowitt weather station for local outdoor readings, frost heads-ups and rain-aware watering.