If I have a small mini-ITX motherboard, then what should I choose for PSU to get low electricity bills?

  • a 250W PSU? or
  • a 60W PSU?

Just for example: A 60W PicoPSU vs. noname 250W PSU? Which would require less power?


Watt is the unit that measures power. But: A 250W PSU can deliver up to 250W. A 60W PSU can deliver up to 60W. Note that they don't always consume that much.

It depends on what components you have and how many Watts they demand from the PSU. Therefore, drawing everything the PSU offers, a system with 60W PSU will consume less power than the 250W PSU.

Generally, get a PSU that fits your components and one that offers as much efficiency as you can get.

See Jeff's 2005 blog post for more details on how to measure that.

Here's a similar Server Fault question: Does a 500 watt power supply always use 500 watts of electricity?

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  • 5
    don't forget the efficiency rating of the PSU ;) – Journeyman Geek Sep 17 '11 at 14:54
  • ...also, the efficiency of the PSU at idle, as the efficiency differs depending on load level (bell curve). – paradroid Sep 18 '11 at 5:11

How much power also does the 12v supply for the 60W PicoPSU waste. You really need to meter it, because you have no idea which is the better performer. Given the highly efficient conversion on PicoPSU and probably same in its uplevel 12V supply (likely fanless where your 250 would start on fire without a fan,) the Pico combo.

But really, the difference is something like 5 watts, so unless you're running hundreds of these, its a trivial power difference. Also the PicoPSU has a dinky 5V rail (5A on the 120W model) versus a standard power supply, so if you power extra devices like a switch and wireless router off the system's 5v rail... Then you're a geek too.

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