Sonoff POW R2 and Tasmota 7.1.0

Itead POW R2 and bulb

Call me slow (and I’m sure someone will) but I’ve had a POW R2 unit lying around for ages and never gotten around to using it. Not only does this unit handle 15 amps (non-reactive – is there such a thing as a non-reactive 15 amp load?) but also does power monitoring.

I’m as averse to using another cloud and another APP as the next techie, probably one reason why I left this board on the shelf. But recently after a love-affair with firmware ESPURNA I’m back to Tasmota – Theo Arends’s increasingly useful open source software which now works on a big variety of devices – more on that elsewhere. Now before we get started, Itead sent me this ages ago to play with and no we do not do tracking or affiliate stuff – or anything at all, they just occasionally send me bits for honest review and I can honestly say this is the first Tasmota conversion I’ve done where the power monitoring actually works. I’m quite chuffed though a 15w lamp is hardly pushing the boat out. (See later – I have a REAL job for this unit).

Itead POW R2

Someone said “can you test it on a tungsten lamp”- I’ve not had one of those for the best part of a decade. I was lucky to find an old compact fluorescent.

Recently, having grabbed the POWR2 board and plugged in my handy FTDI (serial programmer) into the PC and loaded up ESP8266Flasher.exe, I grabbed the latest sonoff.bin and flashed the board. Within minutes I had a working board with no cloud, no APP and my web browser was soon talking to the board via it’s web interface. MQTT will be next, as usual. Do NOT copy my rig – we’re looking at lethal voltages here and I’m using very thin wires because I’m lazy and they were handy.

Oh yes, as well as installing the basic SONOFF.BIN software (see Oct 31, 2019 update in here – the file is now called “TASMOTA”), this one liner is needed… In the Tasmota configuration OTHER web page, drop in this, activate and save. Aftr a reboot you should be all done.

{“NAME”:”Sonoff Pow R2″,”GPIO”:[17,145,0,146,0,0,0,0,21,56,0,0,0],”FLAG”:0,”BASE”:43}

Please note, as of the November 30, 2019 update here, Tasmota is now up to version 7.1.0 and I’ve updated the blog accordingly. Also, the software now has an online manual to replace the old WIKI – that should be worth a look. There is also a new FLASHER based on nodemcu-piflasher – all in THIS seems to be the place to go now for Tasmota documentation.

For a second when checking that board out in late October, I panicked as the output voltage in the web display showed zero, then a friend (ok, Antonio in Italy who also alerted me to the latest Tasmota updates) pointed out that I had the output turned off – silly me…. so off I went in search of a test bulb – the result after turning the output on? – not only did the bulb light up but I could watch it’s power consumption on my never-to-be-copied, unsafe test rig. Power monitor calibration will follow – but let’s not get boring. Next step after wiring this up properly and checking the 15A relay with a 2KW heater, I would soon add MQTT and Alexa – 30 seconds-worth. I’m talking 240v or so, not 110v where you would need higher current capability to handle such a heater.

Yes, I know much of Europe is 220v, but where I live in the UK we get up to 250v.

The box says 3500W max (resistive load) so I’m guessing my office 2KW electric heater should be ok as that is around 8 amps for us of reactice load and the POWR” relay is rated at 15A non-reactive. In fact I’m 100% confident it will be ok. For those who don’t know, heaters ARE reactive loads so don’t go trying a 3.5Kw heater on this.


There’s a photo here from the little manual that comes with the product – for those who don’t want to go down the DIY route.

EWELINK and Cloud use

I started this with Tasmota and at the end of this I’ve upgraded to Tasmota (November 20, 2019) and I just had a thought, it has escaped me up to now… The most powerful item in my office is that electric heater, everything else should pale into insignificance – even my reversable air-con which I seem to recall uses no more than maybe 800w to generate 3 times that amount of cool or heat – well I read that ages ago, now is the time to test… I’ll try sticking my POWR2 device inline with power coming into my office… that way I can prove once and for all how much juice all my little toys take. It may be prudent to keep the heater off initially (I do have a radiator running through here from the house). But I need another POWR2 just in case… more when I get one.


39 thoughts on “Sonoff POW R2 and Tasmota 7.1.0

  1. I’ve got a Sonoff POW running at my holiday home very reliably. It is running Tasmota and communicating via MQTT to my “Pimatic” (NodeJS based Home Automation) system. I use it to control an under-counter water heater – just under 2kW… in fact – according to Tasmota – 8.39 amps at 223 volts (here in the UK).

    It’s been running for well over a year now – powered 24/7 for 10 months of the year and used most weekends and 7 days a week for the odd week here and there.

    I was very cautious at first and tested it at home on lower and then increasing loads, but I considered 16 Chinese amps to be okay with 8.5 English amps (after testing). I’d not run my fan heaters on them as I’d not chance a non-UK piece of kit with a high current inductive load – especially 50+ miles away, unattended.

    Tasmota firmware very reliable – Sonoff POW hardware also very reliable.

    2 x thumbs up from here.

    1. Nice to hear, Darren, thanks for the feedback. Yes, controlling power stuff remotely as against a few bulbs is always something of a leap of faith. I’ve been ok with Sonoffs, never going beyond maybe 70% of their rating (as usually, high loads ARE inductive). I just wish they’d scrap this common line nonsense and just use 2 neutrals with an optional link. Sometimes I want to use them with thermostats or to control something low voltage…. a problem when they have that commoned line to Neutral. I ended up using a Shelly One on my heating stat. Other than that they are great and I love the POWR2 – by tomorrow it will have Tasmota on it.

      1. Correct that -it’s not midnight yet and I’ve put on it using “OTA MAGIC” – took 2 minutes – lovely.

        1. the VERY important part of OtaMagic is to leave the device there for 2 or 3 minutes, as it does its dual flash automaGically… don’t touch, don’t refresh browser, go get a coffee or a pee 😀

    2. Actually fan heaters are not inductive loads except for the low wattage fan motor. The high current heating element is a restive load. In general terms for a load to be inductive it needs to have either windings or some other magnetic influence. Your under counter water heaters are resistive loads.
      However, I consider your decision not to use Sonoffs to control high current loads loads directly very wise.

      1. My heaters are not fan heaters… they are generally oil filled heaters but I take your point – we are both right – better to be safe than sorry. Because the relays are rated at 10 amps, putting 10 amps through them seems like pushing one’s luck to me and by staying 20%-30% below that, up to now I’ve had no issues and only very slightly warm Sonoff units. There is the other question of whether the tracking is up to handling such loads contantly – I prefer non-destructive testing and so far, so good.

        1. For the sake of clarity for others reading the blog most electric heaters are resistive since they are basically a high resistance wire wound around or within an insulated support. This would include oil filled heaters, immersion heaters, kettle elements, oven elements, aquarium heaters, soil heating cables, frost protection cables etc.
          Motors, relays, etc are inductive loads.
          BTW Peter the site seems to have slowed down again, have you noticed anything?

  2. to reflect the fact that it’s not just a “sonoff” related project anymore, but a general purpose firmware, Tasmota moved from 6.7.0.x to 7.0.0.x and git repository and firmwares have been renamed in last days, moving from sonoff-tasmota to just tasmota, and from sonoff.bin to tasmota.bin, and now dark theme is default in web gui

    more info on latest Travis (DigiblurDIY) video:

      1. relevant additions: blinds and roller shutter commands are now native (previously there was a tasmota fork by Stefan Bode):

        support for converting a tasmota device to a zigbee gateway:

        support for up to 3 pzem004t modules to allow monitoring of three phase mains:

        new command POWER0 to turn on/off all relays at once:

        solved issues with Amazon Echo Dot 1 and 2 generation, when using Wemo emulation:

        full console log can now be sent over mqtt:

        and tons of other stuff, look full changelog here:

  3. Thanks for a helpful article Peter. Personally I have never found power monitoring devices very useful – if I have a device switched on it’s because I need to use it, so how much power it is using is not really the issue. However, the Sonoff POW R2 is REALLY useful for saying whether the device IS switched on. Has the Washing Machine finished its cycle (and stopped drawing power)?, for example. Test for that in Node Red and get yourself an automated notification to hang up the undies.

      1. Well, as someone who uses Node-Red on my Raspberry Pi, along with Grafana, I’ll soon be feeding the information into Grafana (via Node-Red) for long term storage.
        I wish they’d do a man-size version as my air-source heating system takes a LOT more than 15 amps…

        1. Hi Peter, I guess you could use a CT device (PZEM-004T maybe) to monitor your ASHP current draw. According to Antonio the new Tasmota firmware has included the PZEM-004T.
          You have also mentioned, I believe, using a camera to monitor your system water pressure. I am intrigued as to why you cannot install a water pressure switch linked to ESPGO with appropriate alert to your phone if the pressure drops.

          1. no, pzem-004t was there from quite a while, now they included the possibility (which espurna has already from more than a year) to use 3 of them indipendently (look at diagram in the relative link in my other comment)…

            remember, you have to 1st connect pzem modules 1 at a time to change their internal address (same format of ip addresses but they’re not ip addressess…) to make each of them unique…

            if you want a single device, boxed and neath, in which you can even hide a wemos d1 mini to have it wifi, then go for the pzem-016:

    1. or you can stop the laundry machine if the oven has been turned on and having both will trigger your mains breaker for excessive power drawn… power metering is the way shelly 2 and 2.5 can understand if a curtain/blinds arrived its endstops, and so releasing the relay… and many other use cases, of course…

      1. Out of curiosity Antonio what is the typical mains breaker limit in Italy. Here in the UK it is usually 100A at 240V on the main breaker with 32A on the ring circuits and 6A on the lighting. And also do they use ring circuits in Italy?

        1. We’ll await Antonio’s answer but It is my understanding that on the continent ring main systems are not common rather they use radial systems.
          In the Uk we have radial systems for Immersion heaters, Cookers, Electric showers etc. some of which are fused (MCB) at 40A or more.

          1. Our radial systems go back to copper shortages after WW2. In Spain they are more inclined to use a spider type setup.

            1. You are correct Peter where a ring main fed from both ends in theory halves the current through each conductor; QED smaller condctors in times of metal shortages.

              Works well while a ring is continuous but one is “skating on thin ice” when a fault exists if I understand correctly?

        2. In Italy the contract most used by home users is 3000W of maximum withdrawable power. But you can get to + 10% more without disconnection. Since the rated voltage is 220 V the maximum current is 3300W / 220V = 15A.

          1. Well, that’s worth knowing. Our heating system here in the UK uses 3.5KW, add 2.5KW for the kettle, 800w for my office air-con (on REALLy cold days add 2KW office rigid heater) and assorted lighting, TV,etc, I’d be in REAL trouble in Italy at 7 or 8KW . I think we have 5KW max in Spain and they don’t cut us off if we exceed, but there is a charge I believe. Our voltage in Southern rural Spain is 220v, where I live in the UK is 250v.

  4. I can take a look at that however here, 248v is not too high. I’ll just whip out my accurate meter….. which is wandering back and forward betweeen 246 and 250v right now…..

  5. you can start calibrating at least voltage, it seems a little too high, i’ve 232V, measured with multimeter and set with the “voltageset” console command in tasmota… and if you know for sure that’s a 11W load, use the “powerset” command, too… done that, the “currentset” is just a matter of calculation 🙂

    then, if power factor is near 1.0, you’re good to go

  6. when you calibrate with a known voltage load, that power factor should be as near to 1.0 as possible…

    that sonoff.bin file you used is OLD (6.6.0, now we are on, sure you had it on your hd or took it from the releases page (which, indeed, contains OLD firmwares…)… use latest from here, but now you need to go for the long run (if not wanting to connect the serial again, which, btw, as stated on that page, DO NOT even think of using ANY gpio for ANY sensor on the POW, or you’re going to have you ElectroBoom moment…)

    if that firmware is based on 2.3.0, then move 1st to 2.3.0 minimal, then to full 2.6.0 one, so:

    suggest downloading both locally and upload them via the firmware page

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