This device is a digital watt-meter allowing you to monitor the power consumption of electrical devices. Its works with both AC and DC current. Regarding AC current, the device computes the real power consumption (not just the product of RMS voltage and current), so it can be used to monitor inductive loads. The Yocto-Watt can compute the power consumption during a given lapse of time. Accuracy is 1mWh, 1%.

This device is isolated, which means that the sensor part is electrically disconnected from the USB part: you can measure any voltage difference between -250V and 250V, without risk of frying your computer. The module provides immediate reading on USB and can also store measures on the device internal flash for later retrieval when connected again by USB.

This device can be connected directly to an Ethernet network using a YoctoHub-Ethernet, to a WiFi network using a YoctoHub-Wireless-n and to a GSM network using a YoctoHub-GSM.

Yocto-Watt Yocto-Watt Yocto-Watt

USB cables and enclosures to be ordered separately.

CHF 110.26

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Hardware release:Rev. D
Product name:Yocto-Watt
USB connector:micro-B
Max current (Cont.):16A
Refresh rate:10Hz
Measuring range (I):-16...16A DC/rms
Measuring range (U):-250...250V DC/rms
Max working voltage:250V r.m.s.
Accuracy (AC, 50Hz/60Hz):0.02 W / 1.5%
Accuracy (DC):0.002 W / 1.5%
Measurement category:Cat II
Protection class, according to IEC 61140:class II
USB isolation, clearance dist.:3.8mm
USB isolation, creepage dist.:3.8 / 6mm
USB isolation, dielectric strength:3kV r.m.s.
Normal operating temperature:5...40C
Extended operating temperature2:-30...85C
Power derating:0,67A/C above 61C
Supported Operating Systems:Windows (PC + IoT), Linux (Intel + ARM), macOS, Android
Drivers:Driverless, no driver needed
API / SDK / Libraries:C++ Obj-C C# VB.NET UWP Delphi Python Java Android LabVIEW
API / SDK / Libraries (TCP only):Javascript Node.js PHP
RoHS compliance:RoHS III (2011/65/UE+2015/863)
Suggested enclosure:YoctoBox-Watt-Transp
Harmonized tariff code:9032.9000
Made in:Switzerland

1 These specifications are for the current hardware revision. Specifications for earlier revisions may differ.
2 The extended temperature range is defined based on components specifications and has been tested during a limited duration (1h). When using the device in harsh environments for a long period of time, we strongly advise to run extensive tests before going to production.

Accessories and related products

YoctoBox-Watt-Transp, Plastic enclosure for the Yocto-Watt sensorUSB-A-MicroB-50, USB 2.0 type A to Micro-B data cable, 50 cm

Related articles and application examples


User manual (HTML)
User manual (PDF)
Product brief
3D file (STEP)
RoHS certificate
REACH certificate
Most recent firmware52757 (01/11/2023)
Programming libraries61813 (07/05/2024)
Command line API61813 (07/05/2024)
VirtualHub application61813 (07/05/2024)

Add a comment 42 comments

1 - funky81 Sunday,may 19,2013 8H38

Currently, I'm planning to buy YoctoWatt to monitor all the wattage in my house. I subscribe for 2200KWH.

Will this thing work ?

2 - martinm (Yocto-Team)Sunday,may 19,2013 8H59

@funky81: actually the 22000kWh value is not sufficient to answer: is it per month? The decisive parameter is the Amp peak. The Yocto-Watt limit is 16Amp. Note that at 16 Amp continuous , the shunt on the board will get pretty hot (~100C). Beyond this limit, the device will become a fire hazard.

So I wouldn't use just one single Yocto-Watt for the whole house. I would use, lets say, one Yocto-Watt per circuit, and I would make sure they are properly cooled.

Also note that Yoctopuce devices are not certified (see Yoctopuce's General Terms & Conditions).

3 - funky81 Tuesday,may 21,2013 22H20

Yup, thats 2200KWH per month. Currently, my house current stable at 7.8Amp.
Since this below 16Amp, will it be sufficient enough to use this product?
Anyway, let me check how many circuit my house have.


4 - martinm (Yocto-Team)Friday,may 24,2013 6H03

@funky81: With 7.8Amp avg you seem to be the safe side. Nevertheless you still need to check for peak consumption. Install your Yocto-Watt and switch on as many big equipment as you can. Check that the total consumption is below 16A. You also need to make sure the Yocto-Watt temperature stay reasonable. DO NOT touch it to check, use a infrared-thermometer or install a Yocto-Temperature in the same enclosure.

5 - blacksmith Tuesday,june 04,2013 13H26

I'm looking for some indication of the storage capacity and the interval the values can be stored. What place can I find this?

6 - mvuilleu (Yocto-Team)Tuesday,june 04,2013 14H33

@blacksmith: You can find this in the user manual, Chapter 19 section 2 (see http://www.yoctopuce.com/EN/products/yocto-watt/doc/YWATTMK1.usermanual.html#CHAP19SEC2 ). The Wattmeter can store up to 500'000 measures. Since each data sample stores 5 measures (DC voltage, AC voltage, DC current, AC current and power), it means you can store 100'000 data samples.

7 - RB Wednesday,may 27,2015 11H19

I have a Solar Charge Controller and I'd like to see how much output my PV (12v 40W) is providing, what my draw on the load is and what capacity my battery is at.

To do this, would I have to purchase 3 of these units, or is there a better product?


8 - martinm (Yocto-Team)Wednesday,may 27,2015 11H36

@RB: One single Yocto-Watt can do all this at the same time.

9 - RB Wednesday,may 27,2015 11H58

@martinm How is that possible as there is only a single Input/Output?


10 - martinm (Yocto-Team)Wednesday,may 27,2015 14H09

@RB: There might be a little misunderstanding here: The Yocto-Watt can give the Voltage, Current, Power, and perform Power integration on a electric connection. If you need to monitor several connections, you will need several devices.

11 - jirkasi Wednesday,january 20,2016 10H55

Hello i need scan instant power comsuption to motor 0,5 kW 230V every half second. Would this work with Your Yocto-
watt device?

12 - mvuilleu (Yocto-Team)Wednesday,january 20,2016 16H00

@ jirkasi: Yes, that should be no problem

13 - southerner Tuesday,april 19,2016 17H44

I have to measure AC loads which peak 50A. May I use a current transformer, as with other instruments?

14 - mvuilleu (Yocto-Team)Wednesday,april 20,2016 9H11

@southerner: unfortunately current version of the Yocto-Watt cannot use an external transformer, as it would have to be used instead of the built-in current sense.

15 - mehdi Thursday,april 04,2024 9H20

Hi, I would like to use this device to track the energy consumption of a machine similar to an AirConditioner. The compressor has a start current of above 20A (AC) and a max current of 8A.
My question Is: can the yocto-watt handle a surge of a few milliseconds (i dont know how long exactly) or not.

16 - mmoram Friday,september 23,2016 7H31

Hi, I would like to measure the power consumption of a mobile phone and of a single board computer (Odroid), would the Yocto-Watt be good for this application? I used an ammeter before inserting it in between the phone and the battery, but I would like to obtain power measurements

17 - mvuilleu (Yocto-Team)Friday,september 23,2016 8H36

@mmoram Yes, that is a typical use for this product

18 - rpb Tuesday,october 31,2017 21H21

I'm needing to measure three phase power. From the user manual it looks like it's just single phase, would I need three units for this?

19 - martinm (Yocto-Team)Wednesday,november 01,2017 5H25

For 3 phases power, it would make more sense to use a power-meter like the one we used here: www.yoctopuce.com/EN/article/monitoring-tectrice-consumption-over-gsm

20 - markb Friday,april 20,2018 0H20

Calibration doesn't seem to work for data retrieved from the logger?

21 - mvuilleu (Yocto-Team)Friday,april 20,2018 5H59

@markb: Yes, it works also when retrieve data from the datalogger (if it does not, it's a bug!). Note however that when retrieving data from the datalogger, the calibration is applied by the API code: calibration parameters are loaded from the device, and applied to each raw measurement retrieved from the datalogger before returning it.

22 - markb Friday,april 20,2018 14H05

Looks like a bug in the API then. I see the exact behavior you describe when I read results directly. But not with the Data logger.

23 - seb (Yocto-Team)Friday,april 20,2018 15H37

@ Mark Brown: I think we should continue this discussion by email. You can send an email to support@yoctopuce.com.
Also in this email could you precise which programing languages you are using and which version of the Yoctopuce library you are using? It could also help if we can have the part of the code that retrieve measure form the datalogger.

24 - pmladenov Tuesday,may 22,2018 8H33

Hi guys,

Is this discontinued or it's temporary unavailable?

25 - martinm (Yocto-Team)Tuesday,may 22,2018 8H38

@pmladenov: it's just temporary: a customer bought the whole stock :-) we had to reorder some parts :-(

26 - amma Sunday,may 12,2019 8H31

Hi I'm relatively new to DOI projects and coding it self.
Now I'd like to communicate with the Yocto-Watt, that is connected via USB micro type b to a Raspberry Pi 3B+ and should be controlled via CLI. My question is:
- is this possible?
And if so:
- Are there any projects done in this area yet?
- or can some one give me a gentle nudge in the right direction?
Sincerely amma

27 - martinm (Yocto-Team)Monday,may 13,2019 6H02

@amma: sure, you just have to use the Command Line library from www.yoctopuce.com/EN/libraries.php . You can find a general description here www.yoctopuce.com/EN/article/new-command-line-api and some Yocto-watt related exemples in the Yocto-Watt User manual.

28 - amma Friday,may 24,2019 9H30

Hi can anyone tell me if the watchdog function at the YoctoWatt is equivalent to relay and if so, can it be used to stop the energy transfer for more than just a moment?

29 - amma Friday,may 24,2019 9H43

HI can anyone advice me on how to proceed?
So my situation is that:
I would like a raspberryPi to host the yoctoWatt and listen via a website to a blockchain and if a specified situation occurs the pi shell start to measure and store the data.

So what is the recommended approach here?
I have though about having the pi host a local website and use the VirtualHub to post the data on some website but im not certain how that works or if there is another approach more favourable?

Many thanks ahead.

30 - martinm (Yocto-Team)Friday,may 24,2019 19H26

@amma: there is no Watchdog feature on the Yocto-Watt. Since you are using a Raspberry PI, you can do what ever you want, like using the VirtualHub to post Yocto-Watt data on the server of your choice or using your favorite programming language and our libraries to build your own solution. If you need help with that, just contact Yoctopuce support directly.

31 - serdan Wednesday,may 13,2020 3H57

Hi, I'm starting to use Yoco-Watt, and I would like to measure the energy consumption of my computer, but I didn't know how to make the connection.
Can you please tell me how to do it or can you make a youtube video showing how to do it?

Many thanks ahead.

32 - martinm (Yocto-Team)Wednesday,may 13,2020 7H08

@serdan: You will find a diagram in the user manual section 2.2. But honestly, if you are planning to monitor a mains powered appliance, but don't know how to connect it, you should ask a professional to do it for you. Wiring mistakes could kill you and/or burn your house down to the ground.

33 - serdan Thursday,may 14,2020 0H51

@martinm thank you for your reply,
I will consult a professional for the connection. However, I just want to make sure that the sensor is suitable for such an experiment? (measure the consumption of my computer)

34 - mvuilleu (Yocto-Team)Thursday,may 14,2020 6H10

@serdan: Yes, the voltage and current consumption of a typical computer is in the operating range of the Yocto-Watt

35 - irfan Tuesday,february 02,2021 16H47

I have two questions please. How to connect Yocto-Watt in three phase line? Are there any multichannel boards available?

36 - martinm (Yocto-Team)Tuesday,february 02,2021 17H27

@irfan : The Yocto-watt is not designed for 3 phases systems. If you have to measure such a system have a look here: www.yoctopuce.com/EN/article/monitoring-electric-consumption-over-gsm

37 - gsel Wednesday,december 29,2021 21H49


I am yet to receive the device. My research will involve using the data generated to analyze for trend in power usage in a computer for different apps/tasks. Since I have not used this before, I would like to see an sample/example of the output from the device? Can you help me with a sample data generated on a laptop/computer please?

Best Regards

38 - martinm (Yocto-Team)Thursday,december 30,2021 6H27

@gsel : since you are supposed to write your own code to extract data from the Yocto-Watt, there is no typical data output format. You will find a programming example dedicated to the Yocto-Watt in each programming libraries (www.yoctopuce.com/EN/libraries.php).

If programming is not your thing, you can use the VirtualHub (www.yoctopuce.com/EN/virtualhub.php) or Yocto-Visualization (www.yoctopuce.com/EN/tools.php) to export data in CSV format.

While waiting for your device to arrive, I suggest you have a look at our tutorials section (www.yoctopuce.com/EN/tutorials.php)

39 - gsel Thursday,may 12,2022 21H03

Hi @martinm,

Thanks, I used the virtual hub to start with to extract data from wattmeter.
This is the output:

UNIX time ISO time power voltage1 voltage2 current1 current2
1652139318 2022-05-10T11:35:18.000Z 0 -0.001 0 0 0
1652139319 2022-05-10T11:35:19.000Z 0 -0.002 0 0 0

All values are zero or negative. I plugged it into the USB console of my laptop. Please let me know if I need to do this differently.


40 - martinm (Yocto-Team)Friday,may 13,2022 3H04

@gsel: negative values means you have either a polarity or power/load inversion in your Yocto-Watt wiring, see


Contact Yoctopuce support directly if you need more help.

41 - mehdi Thursday,april 04,2024 9H25

Hi, I would like to use this device to track the energy consumption of a machine with a compressor. However my starting current (AC) is above 20A. and my max current is around 8A.
My question is: can the yoctowatt handle that starting surge and if yes for how long? i dont know exactly how long the starting surge is.

42 - mvuilleu (Yocto-Team)Thursday,april 04,2024 10H21

@mehdi If this is really just a few milliseconds, it should be fine because it will not have time warn PCB tracks and the current shunt enough to damage them. The analog input is safe, but the peak value will be truncated to the range of the A/D converter

Yoctopuce, get your stuff connected.