Lights reminding you to turn things off

Standby indicators - Duncan DrennanStandby indicators - Duncan Drennan

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?


  1. Jered Floyd

    The one I’ve never understood is the “low battery” indicator light, which is fairly ubiquitous on portable devices. What does this say about the designer? “I’m running low on power, so I might as well burn more of it by turning on an indicator light”?

    The other inappropriate indicator use that I despise is the use of over-powered blue power indicators on video display devices. Both my computeer monitor and my television have a blindingly bright blue LED which is on when the device is on (which should already be self-apparent), and off when the device is off. For a similar area of space the LED is brighter than any part of the display surface, so it’s incredibly distracting. I’ve had to put black electrical tape over the indicator.

  2. Roy

    My digital radio emits a highly irritating buzz when in standby and as the only place I can get reception is next to my bed, it kept me from reading in peace. I have now fitted a lightswitch to the power cord so I can power it down completely when not in use – thankfully it still remembers all my stations and settings, however the perverse feature is, in order to use it as an alarm, the thing must be in standby overnight in ordfer to switch itself on. So now I keep it powered down all day, and switch the power on just as I’m about to sleep just so that it can to be in standby all night to wake me up in the morning. This wouldn’t bother me so much if that buzzing wasn’t a constant reminder of how much energy it is frittering away!

    The question of power and standby LEDs is interesting. My hard drive has a ridiciulously bright power light that illuminates the entire area under my desk, one which I’d rather nobody saw!

    My digital camera battery charger has an LED that switches from red when charging to green when charged. Being red-green colourblind, along with a large proportion of the population, this feature is entirely redundant as the colours are at just the right saturation (suspiciously so) for the difference to be indiscernable to me. If you’re going to add an LED of dubious benefit, at least make it benefit the widest population possible!

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