Power measurements on some (home) computers.

During holidays on one of the rainy days I decided to measure the power consumption of some computers at home and work. I "scored" the domainname "delaat.net" and had implemented the usual services (dns, www, mail, etc.) on MacOSX on a G5. What triggered my measurements was the fact that two laptop screens broke down at work and it seemed not economical to repair it (2 of the 3.5 year old Apple 550 MHz titanium laptops exhibited screen outages and black bands up to the point that no matter what bending the screen the problem would not temporary go away anymore). So I moved to set it up as a screenless server with an external firewire disk. Main advantages are: silent and little power consumption. The big and fast computer can now be easily used by the kids for games without the chance of disrupting service.
Doing the measurements I found very remarkable results. It seems that the new server running uses less power than a G5 turned off! See below and picture for current server.
The setup in all cases was basically a digital multimeter  (Dynatek 9020A) in series with the equipment measuring the AC current. I was adviced to check with an old style multimeter with a magnetic coil and found the same values. I did not correct for a phase shift but do not expect that to be a big effect.

computer test Ampere Watt
  zero offset 0.010 2
  40 watt light on desk, just to check 0.160 33
 

 
G5 screen off, computer unplugged from power socket 0.020 2
2*2.5 GHz screen on, computer unplugged from power socket 0.170 35
20 inch lcd screen computer and screen off, waiting to be turned on 0.180 37
  computer and screen sleep 0.190 40
  computer reduced power setting, idle, screen off 0.800 174
  reduced idle, screen on 0.950 207
  reduced + 3 tasks -> fully loaded both cpu's + screen 1.230 268
  highest power setting or power save automatic + screen + 3 tasks, screen off 1.570 343
  highest -> no power save + screen + 3 tasks 1.730 378




MacMini Duo Intel
 off, only power supply, no screen
 0.043
 9
1.83 GHz
 off, powersupply connected to macmini, no screen
 0.047
 10

booting, no screen
 0.170
 37

idle, no screen
 0.140
 31

very busy on one core, no screen
 0.163
 36

very busy on both cores, no screen
 0.211
 46




Aluminium laptop 15" reduced idle, without accu recharging, screen off 0.070 13
1.25 GHz reduced idle, without accu recharging 0.100 20

reduced idle 0.120 24
  reduced + 2 tasks 0.140 29
  highest, busy, without battery charging 0.160 33
  automatic, busy 0.180 37
  highest, busy, including battery charging 0.190 40




laptop without screen only 200 Gbyte external firewire disc 0.080 15
550 MHz laptop+disk after startup, idle, webcam idle connected or not makes no difference 0.110 22
g4 when webcam accessed, cpu fully loaded 0.140 29

Laptop and disk during startup 0.160 33




IMAC
computer off 0.040 7
1 GHz g4, lcd 17 inch sleep 0.070 13
  startup 0.230 48
  login screen 0.230 48
  idle 0.250 53
  busy 0.340 73
  startup + screen 0.350 75




IMAC-DV computer off 0.070 13
400 MHz g3 sleep 0.200 42
15 inch CTR computer on, screen off 0.240 51
  computer on, screen on 0.400 86
  startup 0.410 88




Airport Express   0.011 2

Photo of currect laptop based server.

Note that the LCD was taken out including the supporting backlight, etc. The screen frame was re-attached for cooling purposes. A (small) part of the heat of the laptop is radiated that way. Note the 200 GByte firewire harddisk next to the wall. That contains the system and all files. In case the laptop breaks down, the service can be brought up again by just connecting the firewire harddisk to another computer and booting from it. The laptop has a gigabit ethernet port build in connected to the 16 port Netgear GS116 gigabit ethernet switch not visible in the picture. File transfer tests show that the limitation is at the disks. Transfer speeds in the range of 25-30 MBytes/sec are observed. Due to its modem port the laptop also enables fax service for the networked users. This all for a mere 22 - 33 W in contrast to the 180 W required by the G5.

Laptop based server