A friend of mine asked me for a temperature sensor for his home. So far, he’d been using the built-in sensor in the Apple HomePod mini, which, in all fairness, exists. But in my opinion, it’s not that precise. So when he asked for my recommendation, I replied that he should get Home Assistant and all the cool stuff. He of course said no: “I only want the temperature sensor, not an entire smart home.” Fair enough.
But he already had some smart home components—the HomePod mini—which supports Thread, and Apple’s smart home platform supports Matter1.
So I went looking for a good temperature sensor. My preference would be a Sonoff sensor, since I’m still convinced they provide some of the best quality at a rather low price. But while Sonoff has intentions to support Matter (and I assume they’ll do that via Thread for battery-powered sensors), they’re not there yet.
So I looked around a bit and found that Aqara has quite a few Matter over Thread sensors, and all of them are Matter certified2. Since I always want to try out new smart home devices, I asked my friend to also buy one for me. Shortly thereafter, they arrived, and I received mine as well.
So I installed it in my Home Assistant, and let me tell you—just as expected, it worked directly without any special configuration. It connected to Home Assistant via the Thread border router in my room, which is also a HomePod mini. My friend also let me know that connecting it to the Apple Home app worked like a charm. The only thing that wasn’t as expected is that it only displays in 0.5° increments in the Apple Home app3.
My old Sonoff sensor (left) and the new Aqara sensor (right)
How good is the sensor?
How well this sensor works is, unfortunately, not super clear. Unlike Sonoff, Aqara doesn’t report the specific sensor used in their devices (Sonoff uses Sensirion sensors), which is a shame. Since I have the devices next to each other, I can compare them directly, but I can’t make any assurances about which is more precise.
Measurement comparison on 19th of July for a full day: Sonoff SNZB-02D is in yellow, the new Aqara W100 temperature sensor in blue.
The good things first: they’re reasonably close together, and in general, the trends are the same. I would consider both to provide accurate temperature measurements (well, accurate enough for almost all purposes). I’m a bit disappointed that the new sensor seems to report new values less often, which makes me wonder why. This is especially strange since sometimes it displays a different value on the screen than what it reports in Home Assistant, which is rather confusing4.
It also doesn’t offer a manual offset (like the Sonoff does), and apparently you can configure the reporting intervals when running in Zigbee mode5. It’s unclear to me why this isn’t possible in Matter mode—I assume it has something to do with Aqara’s proprietary app for their Zigbee hub.
It’s a bit of a shame, but it’s cool to see Matter devices at half the price point of an Eve smart home device.
Buttons!
The device also has three buttons. The buttons are meant to control an Aqara thermostat, which I of course don’t have. I didn’t want to control a thermostat, so my plan was to map the buttons to something else.
My automations and the events triggered in the Home Assistant device info.
The plus and minus buttons I mapped to my air purifier, to increase and decrease the fan inside. And if I double-press the plus or minus button, this sets the air purifier into auto mode, in which it runs most of the time.
The middle button I use as a light button for the big overhead light. This is an Ikea light that is connected by Zigbee. Before, I had a separate button that was directly linked to the lamp (a Zigbee feature); now it goes over the Thread network to my HomePod mini, from there via Matter to Home Assistant, which then sends the signal through Zigbee to my lamp. The Zigbee step probably also has another step in it, since the Zigbee radio is on the floor above, so I’m pretty sure it also jumps through some of the mesh networking. This all goes to say that the reaction is not immediate—I think there is a bit of a noticeable delay, but it is not annoying at all.
So it’s pretty cool that I can also use the buttons directly in my smart home.
Verdict
Overall, the device is pretty cool; the price is very good, especially when compared to other Matter devices. I do wish there were a bit more customization options, but the buttons being exposed over Matter is pretty cool. As for the accuracy, it’s probably accurate enough, but I can’t say for sure.
That’s the thing that’s super cool about standards. You have one device, you can connect something to it, and it automatically supports it. No need for a Zigbee dongle, no need for a new app—just use the tools you already have. ↩︎
I normally wouldn’t care about certification, but Aqara is somewhat renowned for building non-standard Zigbee devices, so I assume that if they’re certified, they follow best practices for Matter. But who knows? ↩︎
This isn’t super unexpected, since the Apple HomePods also return only half-degrees in their app. But now we know for sure that it isn’t just the HomePods—it’s rather a design decision of the Apple Home app. ↩︎
I’m mostly confused because that means there’s more temperature data—it just doesn’t appear to be reported through the Matter endpoint. Maybe this is a battery-saving technique, but since it runs for more than 2 years on the same battery (that’s Aqara’s claim), I would argue it’s fine to update more often. ↩︎
I know I haven’t mentioned it, but apparently you can switch it to run in Zigbee mode, which is pretty cool in my book. Hopefully it’s proper Zigbee and not Aqara’s “we-can-do-whatever-we-want” implementation. ↩︎