Note: the blue line will peak much higher, as soon as I include big modern CRT monitors.

Based on my measurements and some figures found on the web, this is what it's all about: the results in a graph.
Alas I could not measure the original 1981 IBM PC (still had one, but the PSU is defect). But it is save to say the harddrive models would consume about 40 watts and the early floppy-only models even less. (Can anybody confirm this? Please contact me!)
From 1995 onwards the solid lines represent the energy use by low end PC's and the dotted lines represent the energy use by the fastest PC's.
The blue line for monitors does not include big CRT monitors yet. Including these will translate into a large peak in the early years of this century.
The green laptops graph also does not include a large peak in 2002-2005, when many big laptops with desktop processors were build. These laptops run so hot that you can use them to iron your clothes :)
 
My sample of measured equipment is quite small, but the overall trend is clear:

• For over 15 years (!) the energy use by PC's stayed at about 40 watts. In this time we went from the first generation 8088 and 8086 processors to fast forth generation 80486 (80 MHz and plus) processors.
• In the second half of the 1990s energy use starts to rise and the new 'energy saving' options (Energy Star) in hard- and software were in fact never used by most companies and users. Only the few people who implemented these new options were able to lower their energy use a bit for a few years.
• In any scenario: At the turn of the century all new PC's used more energy doing nothing, then a 5 year old PC running at full power ...
• In recent years things got completely out of hand, energy use is sky-rocketing. Using a 'modern' gaming PC in winter however will save you a lot in heating costs :)
  This is also happening in 'datacenters', where our websites and E-mail are hosted. Energy use by servers is even causing a energy and heat crisis in this industry.
• The modern flatscreens are not really saving energy! Yes, they do, compared to you last big 150 watt CRT monitor. But compared to the the monitors people used 20 years back, energy use by computer monitors has doubled!

Of course this isn't progress, but complete madness. Would you buy a new car which uses twice the amount of fuel your current car does? With computers we do, simply because we don't know it. The ICT industry, normally offering us solutions for problems we did not know we had, should help to solve some very real problems for mankind and the world. And finally live up to its progressive imago.
 
All technology to make a PC really energy efficient is already there: For over 20 years, all possible energy saving options are build into laptops. This is done to save the battery, not to save the climate. But of course this could be implemented in desktop PC's too. It's 'off the shelf' technology, and we should demand from industry to put it in our desktop PC's.
 
It's no problem when a PC uses over 300 watts for a few minutes, when you're really busy. But PC's are idle 90-98% of the time they are switched on. So it's in the idle state were the savings must (and can) be made: A idle PC should use no more than 20 watts and with a little extra efford this could be much lower! It's 'win/win' for everyone:

• Industry can brag about helping to save the climate (and rightly so!) and sell new stuff.
• The costs of putting real energy saving options in a PC or server are a few euro's/dollars. This can be earned back in a few months by savings on the energy bill. The rest of the live span of the PC all savings are for you.
• PC's are already a major factor in overall energy use and the number of PC's in use will rise steeply in the coming decades. Energy saving in this sector really helps to save the climate and the urgency to do so rises year by year.

Now the problem is the current 'Energy Star 2007' specification. This is the most important 'standard' for energy saving in PC's. It states that a PC in idle state is allowed to use 50-95 watts. As explained above, that's unacceptable, and quite irresponsible! In this specification the newer multicore based PC's are even alowed to use more energy, not less! This cannot be justified: multicore processors based PC's offer much better options to save energy than the old 'solocore' processors based PC's (allowed to use 50 watt in idle).
It seems consumers, politicians and goverments need to take action, demanding that the ICT-industry shows some respect for the planet ...
 
Boyd Noorda