Can I use Emonpi without internet connection?

Hello everyone!

I have been reading/researching about OEM for a few months now, comparing it against other models out there. I would really LIKE to go with OEM as I hugely support their open source approach. However I haven’t been able to find the answers to a couple questions I have. I would really appreciate it if someone could help me figure them out.

  1. Can I use an Emonpi without an internet connection? I live in house that moves from time to time; I don’t always have internet. I have laptop… could I plug in a USB and upload data? How much data could the SD card of the Emonpi hold?

I did see this article:

However I’m not a programmer; I’m a complete newbie with computers, and I can’t understand much at all about what I would need to do. Is there another, newbie friendly way to configure it?

Thank you for reading and for any assistance in advance!


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Hi Andrew, welcome to the forums. Thanks for your kind works.

Yes, the emonPi will log locally to Emoncms without an internet connection. It’s recommended to add a RTC to keep the time correct EmonPi - OpenEnergyMonitor Wiki

The easiest method to view the data would be to connect the emonPi and your laptop to the same local network via Wifi or Ethernet then log in to Emoncms as normal. This local network does not need an internet connection.

Assuming a generous 10Mb per year per feed and assuming you have four feeds = 40Mb/yr (generous) the emonPi has at least 4GB free for data this would allow for 100 years of data logging!

Or as you have read, it’s possible to get the emonPi to broadcast a Wifi hotspot that you can connect to. However, this method may require a bit more work and technical tweaking

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Hello Glyn,

Thank you for your reply. Indeed about kind words, since you are on the line let me just say bravo on this project. Its relieving to know such competent people are working on the energy crises. I’m inspired to try to incorporate open source building plans (I’m a builder) into my business plan for tiny house construction (Most companies I know keep them private), and I have you guys to thank for passing along awareness of the open source movement to me. Cheers.

Couple follow ups:

To get the Emonpi to broadcast a wifi hotspot, I should follow the instructions in the article I linked in my first post, correct?

If I want to run 6 temperature sensors off the RJ45 expander, how far can I extend the RJ45 cable before I start to lose accuracy? Can this be remedied with a higher voltage power supply to the Emonpi, or some other means?

Many thanks.

Thanks a lot for your kind words. Open source is more fun :smiley:

No, the emonPi has already been configured. You should just be able to start a Wifi hostspot by running

$ sudo wifiAP start

I have documented how this works:

you will need to make this script run at startup if you want wifiAP to start everytime the emonPi is booted.

Please let me know how you get on. I did the work to make the emonPi broadcast a Wifi AP but I’ve not used it since, and I don’t think many other people have so please report any bugs.