Got bored yesterday, so I ran checked out the power consumption of my X3360 system for ****s and giggles with my kill-a-watt.


Powered Hardware Details:

That's it... no other hardware (speakers, monitor, etc.) was in the loop.

Kill-a-Watt Readings
Idle in BIOS screens - 158 W
Idle in BIOS screens with both HDD's unplugged - 144 W

Idle (with speedstep active in XP x64) - 137 W
Load (prime95 v25.6 small FFT) - 213 W
Load (prime95 v25.6 large FFT) - 216 W
Load (prime95 v25.6 blend) - 210 W
Playing Crysis - 237-241 W
x264 encode - 197 W
Standby - 0 W

No real point to this post beyond just trivial information! It is interesting to me that the large FFTs consistently read 3-4 watts higher than the small ones did which is inline with the software's description of the large FFTs as generating the max heat/power consumption. Here is the similar analysis of my older Q6600-based system, but there are too many changes (MB, settings, video board, memory, etc.) for a "which processor is more power efficient" comparison.

What is little bit crazy is that both systems draw the same while idle, and even @ 3.4 GHz, and faster memory, the X3360-based system uses less wattage on p95.

Just goes to show how we don't need these monster power supplies being fired down our throats all the time.

Yeah, I'm not even using 40 % of the 620W I have. As I understand it, the highest efficiency in the PS occurs @ 80-90 % load. On this PS, that would be 500-560 W!

So at 82%(or so for the HX 620W) efficiency your hardware needs what. A max of 200W of the PSUs power output?

An overclocked quadcore and overclocked 8800GTS. WHO NEEDS EPU/DES with such numbers anyway? 3 60W lightbulbs need more energy!

It's a myth that supplies need to be loaded to their max (80-90%) for best efficiency. What happens is the lowest efficiencies are for very lightly loaded supplies, because their power consumption is then dominated by the overhead of the supply simply running itself.

Selecting a supply that will generally be loaded between 20% and 80% of its max is the most appropriate choice. E.g. for a 500 watt supply, the 20% point is an idle power draw of 100 watts on the DC side (or about 120 watts on the AC side).

The power supply reviews over at silentpcreview.com usually have efficiency information in them. E.g. for the Seasonic S12II-380 Power Supply:
http://www.silentpcreview.com/article753-page4.html
peak efficiency (82 to 84%) is from ~150 to 300 watts DC output. Even at ~64 watts DC out, this supply is 79% efficient.