Makers of the Enerjar have posted build instructions to their site. Head on over to start building one of these handy power consumption meters. – Link
Enerjar, Greener Gadgets Design winner on Core77.com – Link
Related:

Greener gadgets design competition results – Link

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This project needs strain reliefs on the cord going through the sharp metal jar lid. There are plastic ones that squeeze onto the cord and snap into a larger hole. Not good to have 120V cord going through a sharp metal hole like that.