The old order changeth, yielding way to new

I was recently looking for a second hand PC power supply for a project which is so late I'm too embarrassed to talk about it.  Whilst walking the dog, I came across a box next to a wheelie bin, I knew it was not a PC, but it was probable that it would contain some sort of power supply, whilst it was not ideal it could save a ride into town.  When I got it home it revealed itself as a CD drive with SCSI connectors conveniently marked as having been acquired in 1993.  Against my better judgement, I powered it up with an energy meter in the line after which it drew a steady 10 watts.  From my experience, this type of device would mainly be used for installing software and performing system backups, when in use it might draw 20 - 30 watts, but only for as long as it takes to write a CD (which in 1993 could be quite a long time).  Back in the 90's a lot of computing was based on servers and local area networks (LANs), there were file servers, print servers, mail servers, database servers etc. etc. spread over one to many grey boxes depending on the size of the enterprise.  At that time I did not take much interest in energy consumption, however for a brief period, three of us worked in my house with a server and some PCs, suffice to say, the central heating was redundant.  Later we moved to offices with a server room which we also used for drying wet clothing.  To summarize, there was a lot of waste heat.

Raspberry Pi - consumption 3 - 5 watts

I'm currently messing with some energy management software which runs on a Raspberry Pi, this device has exceeded expectations, not least because of its energy consumption, I have not done any serious measurements, but I guess it takes something like 3 - 5 watts and nothing is warm to the touch.  The Pi uses a web server to output to my mobile phone.  Like the Pi, the phone is also good with energy.  An aging laptop and an LCD monitor complete my working environment and these are profligate in comparison with the phone and the Pi but even they don't compete with the central heating.

A computing peripheral from the past - Consumption 10 watts at idle.

Another element in computer energy us is the growth of the clouds.  Data centres use a lot of energy but they make it possible to share resources which have been optimised to minimize their energy consumption.  Servers in small offices used to be sized to meet the peak demand, but most of the time (including overnight and weekends) were just a convenient place to keep a mug of coffee warm.  For a few GB of data, cloud storage probably offers a better energy result than operating a dedicated in-house server

Whilst energy costs and footprint have been a factor in the increasing the efficiency of computing devices, equally important is that many applications, most notably the mobile phone won't work unless they are good at energy.

The doctrine of unforeseen circumstances now kicks in, I occasionally heat my work room with a coal fire, sometime augmented with wood I've picked up whilst walking the dog.