Duncan Drennan, who writes the very thoughtful Art of Engineering blog, notes something extremely interesting: standby lights, if they're annoying/visible enough, can actually motivate users to switch the device off properly:
Our DVD player has (to me) the most irritating standby light that I have ever seen on any device. When on, the light is constantly illuminated, but when in standby the light flashes continuously (at a slow rate). This drives me mad, but results in an interesting action – it causes me to turn it off at the plug when I am not using it (which is most of the time). Suddenly one little flashing light has resulted in more energy saving than having no light.
As he notes, designing a system with an indicator which actually draws power to inform you of... 'nothing' ... actually may not be as inefficient as a from-first-principles efficiency design process would suggest, because of that human reaction. Similarly to the Static! project's Power-Aware Cord, you may need to use a little extra energy to make people realise how much they're using without thinking. Although:
There is one problem with this, it only works on people who care. If I did not care about saving energy, then I would just leave the laptop plugged in and the DVD player on. That means that you have to consider how your users will handle this kind of subtle feedback and determine whether turning the light off, or encouraging unplugging, results in more energy savings.
Sometimes the most obvious design decisions may not be the ones which result in the greatest energy saving.
This is a very astute observation indeed.
Are there any other examples where this sort of effect can be usefully employed? How similar is this to the 'useful landmine' concept where you deliberately force/provoke/annoy yourself into taking actions you otherwise wouldn't bother/would forget to do?