IoTaWatt accuracy

Over the past week, I’ve kept a detailed accounting of several channels on two different IoTaWatt that I have in my home, as well as a third that is installed in another site with a PV system. In my home, the town has recently repleced my meter with a brand new electronic meter so they can read it remotely. By definition it is revenue grade. The display has a resolution of 1kWh, so it’s +/- 1kWh. Waiting for a week I’ve used 237kWh so that’s +/- 0.4%.

I also have two electronic meters made by a company called EKM. Here are the specifications. I have these meters on my electric water heater (so resistive load), and on my heat-pump (PF .88-.89).


The solar installation has a Solar Edge inverter which uploads generation to their website and can be viewed through a user portal. Those generation numbers are also used to determine SREC credits.


These are standard IoTaWatt with only the standard voltage calibration. CTs are a mix of SCT019-000, SCT013-000, and HWCT-004, all using the standard configuration data.

There is an ongoing check of an IoTaWatt on the UK power grid that is comparing a pulse meter counter with an IoTaWatt measurement of the same service. Looking to hear of other’s experience.

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Getting my iotawatt real soon here in AUS. In my state of victoria, we have “smart meters” that measure
export (I have solar PV) etc…
I also have Raspberry pi monitoring the Inverter (ABB), so I can get historical generation from the PV system as well.

We can request CSV files of the export/import according to the smart meter.

I plan to place the CT clamps to measure export/import on the main line and also
on the other chosen circuits (I have a total of 12) so iotawatt is perfect for me