Energy efficient power supply for mini ITX board?

[Syringer]

I have this board paired up with a dual core Celeron Dual-Core E1400 2.0GHz CPU, and will be using all the onboard components (HTPC+optical out) mostly for HTPC usage.

Any recommendations for a low energy+quiet solution for this mobo?

Does lower wattage automatically mean it'll use less energy? Is there a minimum wattage I need?

 

[Zap]

You can probably get by with somewhere between 80-120W. In that range you are looking at stuff like the Pico PSU. Those are really dependent on the AC adapter for output quality and efficiency.

Your PSU choice may also be affected by your case.

 

[Concillian]

I'd use this or the ATX sized equivalent (depending on case):
http://www.newegg.com/Product/Produc...82E16817151090

Not THE most efficient, but anything better is quite a lot more expensive, and this is fine for a standard HTPC. PicoPSU is an option, but probably not any more efficient than one of these with the bricks they supply you with.

You can go for something like an x650, which is as or more efficient than the cheaper 300W, even at very low loads (according to jonnyguru testing) but it's overkill at 650W and costs 3-4x as much as the 300W, I really don't think it's worth adding cost. It will however, not turn on the fan if the draw and temps are low enough, so it will be totally silent. The 300W reviews say it's pretty quiet as well, so it should be fine given the purpose.

There's nothing on a spec sheet that will really tell you what you want to know (power draw for your machine will likely be under 80W, but power supplies usually start tanking efficiency under 20% usage. Efficiency specs at 50-60W power just aren't available without looking at specialized reviews.

 

[Syringer]

"but power supplies usually start tanking efficiency under 20% usage. "

What do you mean by this? The less power used the less efficient it ends up being?

I guess I can live with that, if I'm at the point where I'm using too little power where it becomes an issue that's probably a decent problem to have.

 

[Zap]

"but power supplies usually start tanking efficiency under 20% usage. "

What do you mean by this?

A power supply's efficiency is not linear. If someone says a PSU is 80Plus efficient, that just means it hits 80% (or higher) efficiency at three measure points (IIRC something like 20%/50%/80% at 25°C or something like that). PSUs often have an efficiency "hump" in the middle of the output. That's why the higher 80Plus ratings of Bronze/Silver/Gold measure for that.

Anyways, basically an 80% efficient PSU may have something like 82% efficiency at 50% wattage output, and maybe 75% efficiency past 100% output (near where OCP cuts it off) and maybe 70% efficiency at 10% output. Note that I'm making up these numbers, but they illustrate the fact of how current PSUs operate.

Alright, I had to look it up. Wikipedia to the rescue. You should hit the link and look at the chart. They measure at 20%/50%/100% output. Note that starting at the Bronze level, 50% output is required to be higher. Gold, for instance, is 87%/90%/87%.

Read this review of an 80Plus Gold unit. Note the low load test at 10% was 80%, but 20% output jumped to around 87% and 50% output was near 90%.

 

[Concillian]

Here's another example:
http://www.anandtech.com/show/3985/three-550w-psus-for-different-prices/9

10% - 71%
20% - 81%
50% - 84%

If I put my i3 on the IGP, then undervolt and underclock the IGP, my system idles at ~35 watts according to my Kill-a-Watt.

The point is that PSUs aren't really tested down that low, since mostly people don't really run systems at that low wattage. I think it's likely that your system will max out under 80 watts doing linpack (higher CPU load than just about anything else). There aren't reviews that look at power supplies in this wattage range. The best you can do is get a small supply like the 300W 80+ bronze supply that is at least going to be above 80% at 60W. Getting a 450W supply move the rated 20% efficiency point up to 90W, which you might never even hit with your setup.

To some extent efficiency means less when talking about low wattages, just because the absolute waste is less, so maybe it's not an issue, but still sizing should be small. To be efficient at such low wattage requires significant trade-offs and cost (picoPSU 120W, for example, should be at least 80% efficient, but is fairly costly and 120W max plus limited cabling options can be extremely limiting). Most people just opt for something cheap and a little less efficient since even if it's 70% efficient, 30% of a system that idles at 50W is still only 15W of losses, which is fairly easy to dissipate quietly.

 

[Zap]

There aren't reviews that look at power supplies in this wattage range.

Actually, I think SPCR does those.

To some extent efficiency means less when talking about low wattages, just because the absolute waste is less, so maybe it's not an issue

This is a very good point.