2. Log Locally


Local vs Remote logging

Both the emonPi and emonBase feature full local data logging and visualisation capability using our open source emoncms web application - making it easy to keep your energy data within the privacy of your home and without any online service subscription requirements. The local web interface is accessible via the emonPi/emonBase hostname or IP address.

The emonPi and emonBase SD card includes 10 GB’s of data storage enough for 138 years! worth of feed data for our solar PV application (6 feeds at 10s resolution). The software has also been designed to minimise write wear to prolong SD card lifespan.

If you wish to access your data away from home this is possible using remote access services such as Dataplicity. Dataplicity currently offer a free-tier of one device per user. For more information see: Remote Access.

We do also offer an optional remote data logging and visualisation service called Emoncms.org running a slightly reduced feature set to that available locally for applications were remote logging is required. Emoncms.org is a pay-as-you-go service but all OpenEnergyMonitor shop hardware purchases come with 20% free emoncms.org credit which is designed to give 5-10 years of free use. See Log Remotely for configuration steps.

It is also possible to install our open source emoncms software on your own remote server, we have a nice installation script to help with this for use with Debian systems, see EmonScripts.


For application specific input processing see:

The following describes a generic example of configuring an emoncms input, e.g an emonpi power input.

  1. Start by logging in to your emonPi/emonBase http://emonpi/ (or local IP address)
  2. Navigate to Setup > Inputs

You should now see an updating input list of connected nodes (e.g emonPi, emonTx, emonTH) and they keys (e.g. power1, power2 etc.) together with the last received value. If you do not, see Setup > Troubleshooting.

Input data is not saved to disk. To save an input Emoncms Input Processing is used to log an input to a Feed. Feed data is then logged persistently to disk. To log an Input to a Feed:

  • Click on the Input Config Spanner next to the input you wish to log to a Feed:

Emoncms Inputs

  • Process List setup box will open
  • Choose required Input Process e.g Log to Feed
  • Create a new feed giving it a name e.g. use or log to an existing feed *
  • Select the default PHPFINA Feed Engine
  • Select a logging interval e.g. 10s for emonTx/emonpi or 60s for emonTH**
  • Click add to Add to add that input process

Input Processing Power

If logging a Power value input you will also want to create a corresponding kWh Feed. This is done by adding another input process:

  • Choose Power to KWh Input Process
  • Create a new KWh feed e.g. use_kwh *

Input Processing kwh

  • Once required input processes have been added click Changed, Press to Save
  • Then Close the Input List window

Input Processes List View

  • The Inputs page should now display the active input processes in the Process list column

Input View with processing

  • Navigate to Setup > Feeds
  • Updating feeds should now be visible

Feed View

  • To view the feed data click on the feed row
  • This will open the Emoncms Graph module
  • Multiple feeds can be overlayed on the same graph by selecting feeds in the right hand side
  • To view daily data see Emoncms > Daily KWh.

Note: no data will be visible immediately. Wait a few hours to build up some data before trying to view a feed.

Feed Viewer

Using standard feed names such as use, use_kwh, solar, solar_kwh import and import_kwh (case sensitive) will automate the setup of MyElectric, MySolar PV and Android app dashboards. See Setup > Dashboards and Home Energy and Solar PV applications pages for more info.

IMPORTANT: Feed interval logging time should not be less (faster) then the default node update rate. Choosing a longer (slower) update rate is fine and will conserve disk space:

Node Max Update Rate
emonPi 5s
emonTx 10s
emonTH 60s

We recommend making regular backups of local data. See Setup > Import/Backup.