[RKMFlorida]

My first Zotac ION has an external power supply, and I believe it draws less than 30watts while decoding 1080p, or something insanely low.

For my next system, I'm thinking about going with another ION box; however, using a standard PC power supply.

My question is whether anyone knows whether the type of power supply will cause a higher wattage requirement?

Both machines would be *identical* it's simply that one uses the little 12v 50watt external adapter, where as one uses the 150watt power supply that comes with mini-ITX HTPC boxes. I wondered if, despite both boards having the same draw, that the large 150watt supply might use more power than the small, external 12v 50watt supply.

[ion_man]

I depends on how efficient your PSU is, if it's a good quality 80+ certified PSU then it should be about the same. Some PSUs are less efficient at load load though.

[RKMFlorida]

I never realized that the power supply efficiency rating was based directly on the amount being demanded by the system. Now that you say it, it makes perfect sense!

I guess my concern was that a 150watt power supply, even a high-efficiency unit, might have a certain "minimum draw" regardless.

In other words, imagine they test the PSU efficiency of 90% at 180 watts. So it draws about 200 watts for a 180 watt demand. Sure, 90% sounds good in that case. But what about when demand is only 2 watts (sleep mode) or 20 watts (XBMC idle). I'm wondering if that 20 watt overhead remains. In other words, the 90% efficiency is more like 50% efficiency when the system is only pulling 20 watts.

Is this possible, or does the efficiency scale all the way from the 2-watt sleep mode, up to the larger numbers where I suspect they test it?

Thank you in advance!

[ion_man]

Sorry for the late reply, I just realized my previous post has a crucial typo, i meant to say:

Some PSUs are less efficient at low load though.

Generally speaking any PSU is more inefficient at very low loads, so oversizing the PSU is rarely a good idea. Usually best efficiency is around 50%-70% load (rule of thumb, good PSUs can be still very efficient at 25% load too).

[RKMFlorida]

So we're back to the original question... When building an Atom ION system tha draws about 30 watts, is one better using the optional 12v external power supply that can be purchased with a ZOTAC board, or using one of the PC-based power supplies that come in a Mini-ITX case, usually only about 150watt.

From what you're saying, it sounds like "sleep mode" would eat an awful lot more than the required 2 watts, when using the larger power supply. Considering these boxes sit in sleep mode for 80% of the day, it sounds like it might be a better idea to go with the little 12V external power supplies ... On the other hand, I have to assume they are terribly inefficient, is that a fair assumption?

Thank you again for the clarification!

[ion_man]

It's hard to say without testing the PSU with a kill-a-watt, it depends if they are good quality (efficient) or not.
Unfortunately the only way to find out is by trying it yourself or finding a review where they have measured standby consumption.