I mean, a device that will just read, persist, and then push the data to a (my) server without having to buy a 3rd party software license.

The data being, in this case, electrical generation/consumption.

I've been looking at many "smart" meters and data loggers, but the ones available usually come with third party licenses to use proprietary software and such. I've been searching the internet and asking around and some people have told me to just build one myself using raspberry pi or arduinos and clamp meters but I've heard they aren't very accurate (the clamps I mean) and honestly it sounds like reinventing the wheel to me, plus, it would be hard to replicate on my other PV system's projects as I'd have to build every device from the ground up.

I guess on a grand scale the requirements would be:

  • Read info from RS-485 or other industry standard
  • Save it locally (for a limited time)
  • Send it to my server (every minute in the best case)

Do you know any I could use? Or a similar case? How do others resolve this issue?

  • 2
    Welcome to the site! Out of curiosity, what are some of the available ones that you have looked at, for comparison?
    – anonymous2
    Commented Apr 16, 2018 at 20:23
  • 3
    Thanks! I've seriously looked at, at least 25 different smart meters and data loggers. I guess between the ones worth mention, I've looked into Open Energy Monitor, ABB G13, ABB EQMatic, Solarlog, WEB'log and Blue'log. Most include their own proprietary software license to access the data, except for OEM, which looks like a good candidate so far except that it uses clamps for metering.
    – mfdebian
    Commented Apr 16, 2018 at 20:29

2 Answers 2


There is the Sonoff Pow WiFi Switch With Power Consumption Measurement or the SONOFF S31 - COMPACT DESIGN SMART PLUG WITH ENERGY MONITORING that seems to be popular with the DIY community. You can reflash that with new firmware (might not be absolutely needed) and receive mqtt messages on your server. You can then have a TICK Stack to receive and store and graph the data.

  • I am going to look into it, thanks! I will comeback to mark the answer as solution if it corresponds.
    – mfdebian
    Commented Apr 19, 2018 at 13:36

If you already have a digital meter inline (or can fit a cheap 2nd hand one), then you can optically monitor the 1000 impulse/kwH LED which is likely present (without needing to interface to the optical serial port present on the meter). You can then integrate the impulses to approximate instantaneous power.

Bear in mind that you'll need to infer the absence of pulse to indicate instantaneous power accurately if there is a sudden drop in energy consumption.

If you use a 4-terminal meter you can get high resolution measurements, and the meters seem to be cheap 2nd hand when they're out of certification (they're frequently used in blocks of flats). The drawback being they need to be installed inline in the circuit, which might be regulated work (i.e. requiring certification by a competent person).

As regards power, I believe these meters are permitted to consume 2W from the line, and of course you'd need more energy to sample/transmit the signal.

  • Great answer! Just to clarify: what exactly do you mean by "might be regulated work" in the last paragraph?
    – anonymous2
    Commented May 20, 2018 at 14:05
  • 1
    In the UK, if it's not got a plug on it, you're probably not supposed to change a circuit, except maybe replacing an existing light fitting (unless in kitchen/bathroom). Commented May 20, 2018 at 14:07

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