Technology that helps us live within ecological limits

The OpenEnergyMonitor System

System Overview

The system is an open-source monitoring system with the capability to monitor electricity, temperature, humidity and interface with pulse output utility meters.

The system is fully open source both hardware and software with documentation on everything from AC theory to sensor circuit design and application programming available on the website.

Emoncms is a powerful open-source web application for processing, storing, visualising energy and environmental data. One common application of emoncms is to explore historical electricity consumption data, zooming in at any point, either to see instantaneous power over seconds, minutes or hours or to see daily kWh use.

Online Store

The OpenEnergyMonitor system is available through the OpenEnergymonitor Shop

Megni and OpenEnergyMonitor

Megni energy monitoring is run by Glyn Hudson and Trystan Lea. We are based in Snowdonia, North Wales. We are both also founders and core developers on the OpenEnergyMonitor project. The OpenEnergyMonitor project is its own entity separate from Megni it is an online open source community project with many developers from around the world contributing and using the technology for all sorts of different applications.

Our Values

Technology that helps us live within ecological limits.
The development of the system and its application is guided by the motivation to make the transition to sustainable energy in our own lives, we started by optimising electricity use in our own homes and understanding the contribution of solar pv generation, increasingly development is on measuring the performance of building fabric and sustainable heating systems and optimising the use of heating systems.

We use open-source technology developed by ourselves and others as a part of the OpenEnergyMonitor project. We believe open-source is a better way of doing things. You can learn more about this, how the technology works and how to build, repair and improve it, on the project website:


We are based in the mountains of Eryri (Snowdonia) North Wales and we stayed here because of the mountains, we are keen climbers and mountain bikers. Thanks to the internet we enjoy developing open hardware and software and running a technology business from here too.

Glyn's blog:

Trystan's blog:

Twitter: @trystanlea, @glynhudson, @openenergymon