External vs Internal PSU / Power Consumption

[JVervekken]

Is there a difference in power consumption between an external power supply unit (brick) and an internal psu?

If I look at some Zotac boards I see some of them have an external PSU, is this better/worse?

I read a review of a guy that built his own htpc using an zotac ionitx-a-e board (with an external 19v power supply) had a power consumption of 18W even if the system was offline. So he claimed the powerbrick itself consumped 18W even if the system was disconnected??? Seems very strange to mee or is this correct?

Review is here but it is in Dutch :-(
http://tweakers.net/productreview/13305/zotac-ionitx-a-e.html
(look at the power consumption graph in the middle)

 

[00Roush]

I believe the external power supplies are usually more efficient than internal at lower power levels. But this could be more related to the power output of a given power supply. A higher rated power supply usually has a lower efficiency at lower power levels. For example a 800 watt power supply might be 60% efficient at 100 watts but a 200 watt power supply might be 85% efficient at 100 watts. Generally external power supplies have a lower power rating than most internal power supplies and therefore might have a higher efficiency at 20-30 watts.

As for the power brick using power when the system was off... That doesn't happen to me with my power brick for my laptop. On uses about 29 watts and in hibernation it uses about 3 watts.

00Roush

 

[odoketa]

It very much depends on the manufacturer, and will change over time. I had an old Mac that ate over ten watts when everything was off - I don't think it did that when it was new (though I suppose it could have been flawed from the start).

Generally speaking, cheaper stuff comes with cheaper power supplies, which are less efficient. The internal / external thing is, I think, something of a red herring. Usually external packs are used for items requiring less power, and are therefore built to be more efficient at lower power draws. Internal packs are used for heavier loads, and are therefore built to be more efficient at higher power draws. More than likely the manufacturer will chose one that is appropriate to the expected load.