SONOFF TRV Gen2: what changes for a Zigbee heating setup

SONOFF has a second-generation Zigbee radiator valve. The TRV Gen2, model TRV-ZBT, went up on SONOFF’s own store on August 20 with a launch guide the same day. It is smaller than the TRVZB it follows, it has a colour screen, and it costs $7 to $8 more depending on the storefront.

Short version: if you run Zigbee2MQTT and you have hydronic radiators, this is a reasonable upgrade, and Zigbee2MQTT already exposes more of it than it does of the old valve, down to calibration state and the stored heating history. If you run ZHA, the blocker has partly lifted: a stopgap quirk shipped in zha-quirks 2.4.0 on October 28, so the valve is matched rather than ignored, while the pull request that adds full support is still open and SONOFF’s workaround for the rest is a script. And nothing here retires the first-generation TRVZB, which is still on sale for less money.

What SONOFF shipped

The two spec tables, side by side, as SONOFF publishes them:

Those prices and stock states are the same as when I first read them on September 20.

SONOFF’s headline claim is that the new valve’s volume drops 38%. The arithmetic on those two dimension rows gives 38.2%, so the claim matches its own spec sheets.

One row is worth a footnote. SONOFF’s marketing copy calls the new valve “Built on the Zigbee 3.0 standard”, while its spec table lists only Zigbee and IEEE 802.15.4 where the old valve’s table says Zigbee 3.0. Either way both are ordinary Zigbee devices that join a Zigbee coordinator; SONOFF’s page says a Zigbee gateway is needed.

The feature list adds three switchable heating plans of up to 12 periods each, automatic open-window detection that works from a temperature drop with no sensor at all, sensor-linked detection using a SONOFF contact sensor, six months of stored heating history, and software valve calibration you can re-run from device settings without re-pairing.

Two things went the other way. The setpoint range narrowed at both ends, from 4C to 35C down to 5C to 30C. And the valve now runs on two AA cells instead of three, with SONOFF quoting up to six months and discouraging rechargeable NiMH cells on voltage grounds.

One label on the spec table will trip people up. The row reading “Thread Connection, M30x1.5mm” is the mechanical thread that screws onto the radiator. The only radio on the spec table is Zigbee, and SONOFF’s own Apple Home route goes through a Matter bridge, so I couldn’t find anywhere that says this valve speaks Thread or Matter itself.

What stays local and what does not

On Zigbee2MQTT

This is the good half. Zigbee2MQTT lists the TRV-ZBT with a long exposes list: setpoint, local temperature and calibration, running state, battery, fault status, frost protection, child lock, an external temperature input, heating and idle valve positions, valve travel calibration, the schedule groups, open-window state, heating percentage per hour, and the stored temperature history. It supports over-the-air firmware updates too.

The first-generation page is shorter: the TRVZB exposes valve opening and closing degrees and a weekly schedule, but nothing for fault status, calibration status, the schedule groups, or history.

SONOFF asks for Zigbee2MQTT 2.12.1 or later for full support. That release went out at the start of July, and the current release is 2.14.2 from October 1, so anyone reasonably up to date is already past it.

On ZHA

SONOFF’s own product page says a pull request adding full native support to ZHA “has not yet been merged”, and that until it is, “some device capabilities may not be available through ZHA out of the box”. Its answer is a script from the SONOFF help centre, and it says the same applies to SmartThings.

That pull request is #5234 in the zigpy/zha-device-handlers repository, titled “Add quirk for SONOFF TRV-ZBT”. It was opened on August 7 and was still open when I checked on October 14. Its description lists what it adds: thermostat controls, device configuration, diagnostics, temporary mode, weekly schedule, Bluetooth pairing and motor calibration. That is a fair guide to what a ZHA user may be missing today, though I haven’t seen what ZHA shows without it.

SONOFF’s other article muddies this slightly: its walkthrough for feeding a room sensor’s reading into the valve has a ZHA branch that assumes an external-temperature number entity on the ZHA device page. So part of the device clearly does work under ZHA.

The Bluetooth side door

The new valve also pairs over Bluetooth to SONOFF’s eWeLink app, which is how SONOFF suggests you edit those three schedules when your platform cannot. SONOFF is clear that this does not replace Zigbee, does not remove the device from your Zigbee network, and does not wipe its settings. The same channel does firmware updates for people whose platform offers none.

It is a sensible escape hatch, and it runs through a vendor app. I couldn’t find anywhere that says whether eWeLink needs an account to do it. If a vendor app touching a device you paired locally bothers you, the schedule entities are in Zigbee2MQTT anyway.

Apple and Google

SONOFF’s page routes Apple Home through a Matter bridge and names the hardware that can be one, including its own iHost. That is bridged Matter, not a Matter device, which means the bridge is a single point of failure between the valve and Apple Home. I couldn’t find Google Home named anywhere on the product page.

Buy, wait or ignore

Home Assistant house on Zigbee2MQTT. Buy, if you have M30 x 1.5mm radiator valves and you want per-room heat. You get more control surface than the old valve gives you, and it joins your existing coordinator with no SONOFF hub. Check ITEAD rather than the US storefront, which still showed sold out on October 14.

Home Assistant house on ZHA. Weigh it rather than wait outright. The interim quirk in zha-quirks 2.4.0 means a fresh pairing is matched instead of ignored, but the vendor still calls ZHA support incomplete and still hands you a script for the rest, so check which zha-quirks version your Home Assistant release bundles and whether pull request #5234 has merged before ordering. The Zigbee2MQTT and ZHA comparison covers what moving would cost instead.

Apple Home or Google Home house. Ignore, unless you already run a Zigbee bridge that exposes devices over Matter. That is a lot of moving parts for a radiator.

Budget buyer. Buy the old one. The TRVZB is $26.90 at ITEAD against $34.90 for the new valve, it is still stocked at both of SONOFF’s storefronts, and Zigbee2MQTT supports it too, OTA updates included. The colour screen and the history graph are nice; they are not $8 of heating.

For pairing, calibration, the room-sensor automation and the current state of ZHA support, see my TRV Gen2 setup guide for Home Assistant.

Does this change my picks?

Not yet. Nothing here needs a pick pulled.

• SONOFF TRVZB catalog page. It stays. The product card on this page is the first-generation valve, not the TRV Gen2 I am writing about. Two things there need the owner’s eye: the listed price of $35 to $45 is above the $27.90 and $26.90 I read at SONOFF and ITEAD on October 14, and the page should eventually gain a successor note. Neither is a job for this brief.
• Local-control thermostats guide. The hydronic-radiator pick there is the Eve Thermo, chosen for Matter over Thread and on-device scheduling. A Zigbee valve is a different trade, and the new SONOFF does not displace it. Worth a second look when the ZHA question resolves.
• Zigbee2MQTT versus ZHA. That comparison says Zigbee2MQTT tends to expose more device-specific settings. This launch is a clean example of the gap, and of what it costs you in the first months of a new device.
• Sensors. If you want the sensor-linked window detection, SONOFF names the SNZB-04P among the compatible contact sensors. For the external room temperature, SONOFF’s walkthrough uses an SNZB-02DR2, which is not the model the card here shows, but it says any sensor that reports temperature correctly in Home Assistant can be set up the same way, so the SNZB-02P on that card should work too.