Home Assistant ZBT-2 Zigbee and Thread Coordinator Review

After releasing the Home Assistant ZWA-2, widely called the most performant and optimized Z-Wave and Z-Wave Long Range antenna, the Nabu Casa team is back with something new for us Zigbee users. The Home Assistant ZBT-2, a Zigbee and Thread coordinator and an official successor to the original SkyConnect dongle (ZBT-1).

The first question everyone wants answered is simple. What’s different about this coordinator? What’s better, what’s improved, and what does it bring to the table that others do not? Is it actually better than what you already have from SMLight, Sonoff, or the ZBT-1?

In this article, I’m sharing my experience with the new Home Assistant ZBT-2 Zigbee and Thread coordinator. This is a single-SoC device based on the EFR32MG24 chip, which is an improved and more powerful version of the MG21. You can get it through various Nabu Casa partners, including Apollo Automation (US), Domadoo (EU) and Seed Studio (Global).

Home Assistant ZBT-2 Technical Specs

Device Overview and Disassembly

The Home Assistant ZBT-2 ships in a simple cardboard box containing the device with its antenna, a user manual, and a USB-A to USB-C cable. Everything is neatly slotted inside so it doesn’t shift around and stays protected during shipping.

After removing four screws and opening the base, you’re immediately greeted by the main PCB. The first thing you notice is the antenna mount in the center, which uses a standard SMA connector just like the ZWA-2. This connector is surrounded by several LEDs that serve as status indicators for the ZBT-2. On the left side sits the EFR32MG24 Zigbee/Thread chip, and just below it is an SWD interface that can be used for debugging or flashing firmware. Above the chip, you’ll find a TagConnect interface for the Zigbee/Thread chip, typically used for programming during development or manufacturing.

At the very top of the board are the ESP GPIO pins, which provide direct access to the ESP32-S3 module. These can be used for tinkering, custom firmware, or interfacing with the device at a deeper hardware level. Everything is neatly laid out and clearly labeled, making it easy to identify each component and understand what it does.

The EFR32MG24 [Datasheet] SoC used in newer Zigbee and Thread coordinators like the Sonoff Dongle Plus, Dongle Max and the SMLight PoE models brings noticeable improvements over the older EFR32MG21. It comes with more RAM and flash which gives coordinators extra headroom for larger routing tables and more stable networks. The MG24 is also built with better RF sensitivity and overall radio performance which helps reduce packet loss and improves range in busy 2.4 GHz environments.

My experience tells me that in practice, very few people will notice a major difference between the EFR32MG24 and the older EFR32MG21. The EFR32MG21 is already more than capable of handling large networks and routing tables without any trouble. Still, if you have the option to get the latest and greatest hardware, there is no real reason not to.

The backside of the PCB contains the ESP32-S3 [Datasheet] chip. This handles the USB to serial communication for the coordinator and provides additional processing power for tasks such as firmware loading and other features. It also exposes a set of GPIO pins on the top side of the board for anyone who wants to tinker with the module directly. The USB-C port is mounted at the bottom and serves as the main power and data connection for the ZBT-2.

Home Assistant Integration

Setting up the ZBT-2 in Home Assistant could not be easier. The device works with ZHA, Zigbee2MQTT, and OpenThread, and depending on which one you choose, the setup flow changes slightly. It also has its own official integration in Home Assistant, which handles firmware updates and, more importantly, provides a simple and intuitive onboarding process.

If you are using Proxmox, don’t forget to passthrough the device to the VM.

When you plug in the ZBT-2, it is automatically discovered by Home Assistant. You can then choose whether to set it up as a Zigbee coordinator or as a Thread adapter. Here’s an example of the setup flow:

ZHA

If you are using ZHA, you can either follow the recommended settings or use the migration wizard. This process updates the firmware automatically and completes the ZHA setup in your Home Assistant instance. Once flashed, ZHA gets auto-discovered and you are done.

At the moment the ZBT-2 uses EmberZNet Zigbee firmware version 7.4.4.3 in ZHA. This is not the latest ember firmware, but it appears to be latest one for the ZBT-2. Regardless, the device pairs and works flawlessly.

Zigbee2MQTT

For setting up the ZBT-2 with Zigbee2MQTT, you select the Custom option during the onboarding process. Home Assistant will automatically flash the required firmware so the adapter can be used with Z2M. Once the process finishes, you can point Zigbee2MQTT to the newly created serial device. I used the following configuration to bring up a testing instance in Zigbee2MQTT:

serial:
  port: /dev/serial/by-id/usb-Nabu_Casa_ZBT-2_10B41DE58F04-if00
  adapter: ember
  baudrate: 460800
  rtscts: true

Matter and Thread

And finally, to set up Thread, select Use as Thread adapter in the configuration wizard. This option automatically flashes the firmware, downloads and installs the Open Thread Border Router add-on, applies the correct settings, and starts it up right away. Thread and OTBR are then auto-discovered in Home Assistant, and you are ready to go.

The ZBT2 currently runs OpenThread RCP version 2.4.4.0, which is not the newest release. Silicon Labs has already published version 2.7.2 as their latest OpenThread build, but that does not mean every vendor has adopted it yet. In fact, many devices ship with slightly older but fully stable stacks that have been tested and validated for their hardware. Even with 2.4.4.0, the ZBT2 performs perfectly as a Thread Border Router and shows no issues in day to day use.

Forming and testing a Zigbee network

To truly test a coordinator like the Home Assistant ZBT-2, you would need a very large Zigbee network to push it to its limits. Theoretically, the EFR32MG24 can handle up to 200 routers, and a total network size of 500+ Zigbee devices in a well-built mesh. However, the health and responsiveness of the network will ultimately depend on many other factors such as:

• The number and placement of mains-powered Zigbee routers.
• Wireless interference from WiFi and other 2.4 GHz signals.
• Electromagnetic interference from other devices and adjacent USB ports.
• Proper Zigbee channel setup and other factors.

Learn how to build a robust and reliable Zigbee network.

In my testing, I paired a handful of Zigbee devices and monitored responsiveness and LQI values inside Zigbee2MQTT. Besides checking device compatibility in ZHA, I rely on Zigbee2MQTT as my daily driver, so I formed a small network in my office with random Zigbee devices from different manufacturers. An almost identical network was previously running on the SLZB-06M, which uses the older EFR32MG21 chip.

I monitored the reported LQI and tested the responsiveness of the mesh while moving several end devices around the office. Reactions to commands were instant, routing remained clean, and link quality stayed consistent throughout the testing. However, reactions were also instant and bullet proof with the SLZB-06M. Both devices reported an LQI within 5 points of each other, without noticeable differences.

Furthermore, the Home Assistant ZBT-2’s antenna has a peak gain of 4.16dBi. This number is comparable to the 4dBi on the SMLight range and the 4.5dBi on the Sonoff Dongle Max. Meaning, either of these dongles should theoretically provide a similar network range and coverage. Now, the HA guys do claim the ZBT-2 antenna is perfectly fine-tuned and optimized, and I’m inclined to believe them.

Even though this is not scientific lab-level evidence, my takeaway is this: The ZBT-2 has the newer MG24 chip and offers more theoretical headroom with a great antenna, but in a medium and even large Zigbee networks, the practical experience remains largely the same. You should expect smooth behavior regardless of which coordinator you choose.

Final Thoughts

The Home Assistant ZBT-2 is a well-designed and highly capable Zigbee and Thread coordinator that builds on the strengths of the first-generation SkyConnect. Its updated MG24 chipset, optimized antenna and improved internal performance make it a reliable choice for anyone starting or expanding a Home Assistant setup.

In day-to-day use, the ZBT-2 performs on par or slightly better over other MG21 and MG24-based coordinators. Network responsiveness, LQI values and overall behavior remain consistent with what you would expect from high-quality hardware. While the upgraded chip and 4.16 dBi antenna offer more headroom for very large networks, most smart homes with fewer than one hundred devices will see little difference compared to strong alternatives from SMLight or Sonoff.

The biggest drawback of the ZBT-2 when compared head to head with the SMLight range or the Sonoff Dongle Max is the lack of PoE. For many users, this is a decisive factor, since PoE allows you to place the coordinator in the optimal spot without relying on USB cables or worrying about USB interference. While external PoE to USB adapters exist and can work reliably, it is still not the same as having PoE built in.

With that said, it’s also worth mentioning that while you can technically run Thread over an Ethernet-based setup, it is not recommended. Thread expects a direct serial connection to maintain proper timing and reliability, and introducing Ethernet into the path can add latency or instability.