Open Energy Monitor
= This is a project to develop and build open source energy monitoring and analysis tools for energy efficiency and distributed renewable microgeneration.
" the "OpenEnergyMonitor" initiative, which consists on an open source system (hardware and software) that is affordable and simple to build.
The system is based on the very popular platform Arduino (open source hardware), and on some pieces of software done by the "OpenEnergyMonitor" community. Anyone can visit the website, download a list of the components and the plans, buy them, assemble them, download the software, and tadaaaaa!!! Your own Energy Monitor is operational.
It is possible to monitor many generators/consumers of electricity, natural gas, water consumption, and some other parameters like temperature, luminosity, humidity, wind speed.. etc." (http://www.ulule.com/kirikou-an-open-source-electricity-monitor/)