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The original was posted on /r/homeassistant by /u/BackHerniation on 2026-08-16 12:15:30+00:00.
A couple of weeks ago I shared a comparison of 12 of the most popular Zigbee temperature and humidity sensors I could find online. Someone asked me in the comments for low-temperature data, basically how these sensors would perform in winter or low-temperature conditions.
As it's summer here, I only had one real option: stick them in my fridge, on the shelf right under the eggs.
12 Zigbee sensors in my fridge + a calibrated BLE sensor
Before anyone gets mad or something: I'm fully aware none of these sensors are waterproof and none of them are meant to live in a fridge. But since it's summer here, that was the only cold option I had available. My fridge is set to 5°C and cycles naturally, going up to about 8°C before the compressor kicks in and drops it back below 5°C, roughly once an hour.
My first issue was connectivity. The fridge nearly drowned out my Zigbee mesh completely. My coordinator was sitting about 6 to 7 meters away, and stacking every sensor on top of each other sure didn't help either. I ended up moving the coordinator temporarily to about 1.5 meters from the fridge, which gave me solid LQI across the board and allowed me to collect the data reliably. The BLE sensor also had trouble advertising outside the fridge, I also had to move a bluetooth proxy closer to be able to capture its readings.
Here's what I found:
Least accurate in the cold: ThirdReality 3RTHS0224Z, Tuya UZ-01T, Tuya TH01, Tuya IH-K009 and eWeLink TH03YZ consistently read higher than my benchmark sensor. The ThirdReality was the worst offender, choppy reporting with gaps up to 6 hours between updates, even after replacing the batteries. The Tuya UZ-01T followed the trend of the cooling cycle fine, but consistently read the highest temperature of the whole group.
Most accurate in the cold: Aqara WSDCGQ11LM, SONOFF SNZB-02B, SONOFF SNZB-02P, Zemismart TS0201, Moes ZSS-S01-TH, Tuya TH09Z and Tuya ZTH02. The Zemismart occasionally dipped below 4°C at the bottom of the fridge cycle but follwed the climb back up pretty accurately. All 12 followed the fridge's cycle closely, so the real differentiator was stable connectivity and reporting rate rather than raw accuracy.
Humidity in the fridge: ThirdReality 3RTHS0224Z, Tuya TH09Z and Tuya ZTH02 were the worst here too. The ThirdReality again had abysmal reporting, even though it reported a solid LQI in Zigbee2MQTT. the Tuya TH09Z had the worst accuracy of the whole group. Everything else reported close to my benchmark sensor, humidity was actually more consistent across all of them than temperature was.
Summary: If you actually need a sensor for a fridge or freezer long term, don't use any of these, none of them are designed for that kind of humidity and condensation. You'll likely kill the electronics very fast. You are better off using a Dallas probe sensor, something like a DIY ESP32 device or the Sonoff SNZB-02LD. This was purely a test to see how each one handles temperatures outside its comfort zone, not a real-world recommendation. If you are just looking for a good sensor that can perform reliably in low-temperatures without condensation, pick one of the Sonoffs and be done with it.
For anyone interested in the full article from earlier, you can find it here: