What type of devices are used to measure power consumption?

What type of devices are you using for measuring power consumption of non-light consumers?
What accuracy are you happy with?
Any DIY-ers for this type of function?
Any hints appreciated?

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I’m using the Brultech GEM for my house, I know others here are as well. It is quite accurate, and reliable. I log all 32 energy and 4 temp channels to influx over MQTT. I could use a second GEM, since all energy channels are taken, but it is a bit down on my priority list…

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Check out https://openenergymonitor.org. They offer kitset/Arduino based shields and standalone devices. Very active community and very helpful chaps on there. I have been running a node here for my energy monitoring for 2 years - very accurate and reliable. I modified mine to publish readings over MQTT so very easy to integrate with openHAB.

Definitely worth a look if you like a bit of DIY.


Do you live in North America? Do you know if open energy monitor stuff is appropriate for there.


I live in NZ - so we have 240V supply. From what I understand there are many US users so I am pretty sure their stuff works just fine.

I agree with Ben openenergymonitor is a good solution if you want to diy, using it since 10 months now. My most reliable component so far.

I bought their RFM69 module (RFM69Pi 433Mhz Raspberry Pi Base Station Receiver Board [RFM69Pi_433]) to put on my Pi, the Pi is running openhab and emonhub, emonhub communicate the data by MQTT to Openhab. I’m not using emoncms.
The sensor is the emontx arduino shield (emonTx Arduino Shield SMT [TXSHIELDSMT]) that I put on a clone arduino, communicating to the pi by 433Mhz thanks to the RFM69 module.

I use a modified version of this: http://www.instructables.com/id/Physical-Home-Automation-Interface/step3/Sensor-Energy-Monitor/
It can be made with a Arduino with a ethernet shield. The current transformers can be bought cheap on Ebay or other “China” sites.

Are these sensors very accurate? I only know power meters with direct connection. Also with this sensors only the phase is measured. My power meters measure phase and the blue wire too (in germany it´s called “N” Neutralleiter)

So how accurate can this sensors be?

And can i measure my main power line with this too? It has 3 phases.

thanks, and keep it coming…

Yes, openenergymonitor works with 120V…
And I should have said: I am in Australia – meaning, mostly one phase… but still the same, it needs to be measured.

The princip of current transformers can be very accurate, but i’m not sure how accurate it is in a DIY setup, i think that they may need som calibrating, but it should be accurate enough (depending on what you will use it for).

You only need to measure the phase, it is the same current that runs through the phase will run back through the neutral. The only reason for measuring the neutral would be if you want to monitor for any earth leakage currents (but that would you not do in a DIY home automation setup).

Yes you can use it to measure your mains, but you will need a transformer/sensor for each phase. You can connect multiple sensors to the same arduino (i’m currently using three)

I want to get a real time power meter to see how much watt my house is consuming at the moment.

Can i make this with this setup? Also with small devices which only need about 10 watt?

If i unplug the charger of my phone i want to see in real time that there is less power consumption.

The problem with the one i’m linking to, is that it only measures current, and then calculates the power, therefore it doesn’t account for any voltage drops or deviations.

If you want it more precise, you have to find a solution where both the current and voltage are measured.
I’t looks like the Open Energy Monitor project can do that, so maybe that would be a better solution for you.

Yep OEM takes readings from the CT sensors and an AC voltage sensor (via a standard wallwart plugged into a household socket). It then calculates the real power to give a very accurate value.

My monthly total is usually less than 1% out from my utility bill total - so very accurate IMO.

Are you guys lucky enough to have a power socket close to the fuse box ? I checked all the above solutions and of course they require a socket (no surprise there) but unfortunately there is none close to the main fuse box.

Yep when I got solar PV installed and the electrician wired up the grid-connected inverter, I got him to put a power socket right next to my distribution box.

I use lightwave so have an rfxcom radio http://www.rfxcom.com/en_GB

Because i had this i was able to get a cheap energy monitor from ebay for less that £20 and it seems to work fine. http://www.theowl.com/index.php?cID=185

Had a bit of fun around displaying the correct Kwh and adding up costs but managed to cobble together a rule to do that. Final result was a nice mobile view i could review…

I might add though that these monitors are not amazingly accurate, but its close enough for my needs