This DIY presents a device capable of detecting the stand-by mode of low-consuming electronics in your home (like plugged-in phone chargers, without the phones attached) etc. The metering starts when the devices enter stand-by and stop when they start consuming in large amounts.
The device is made of an energy meter and a current gauge, monitoring the current of mains supplied devices and start/stop metering. The Instructables user who published the article also has an improved version of the control box that is able to set the hysteresis level (threshold) by using a potentiometer.
You can find the instructions on how to build it and the schematics here. In my opinion, saving energy where possible is as important as producing more of it, with the difference that saving is a lot easier to do – it only implies good will – while generating in excess needs money.