It turns out that, with all hardware set up as it is by default, the server draws around 25 Watts when idle and around 40 Watts when under load. To put this into perspective, my desktop PC draws around 90 Watts when idle and around 145 Watts when I'm gaming. Thus, my server isn't incredibly low power as it stands (though this is partly because I designed it to be able to provide some decent number-crunching ability when needed). The total draw over a year will be around 219 kWh, which should cost in the region of £25 or so if my maths is correct.
Bonus power draws:
- 21" LCD screen: 40 Watts
- External hard drive: 10 Watts
- Speakers (silent): 5 Watts
I will update this post in the near future with power draw figures with alternate configurations (such as running the CPU with a single core).