Regarding PSU Efficiency

[NRST]

I've heard that PSU efficiency is about 60 - 80% of it's load. What does that mean?

 

Planning to build a new pc for multimedia, after using pcpartpicker.com the TDP totals at 214w.

Should I take the 400w PSU or 450w?

 

Parts: https://pcpartpicker.com/user/NRST/saved/JJKzyc

(Is that how you link it?)

[Electronics Wizardy]

PSU's don't have one efficency, it changes with load(and tempature, and input voltage) The psu is more efficent from about 60-80% of its max, any more and its less efficent, and any less its less efficent aswell.

 

For a lower power pc like that, Id get a 300w or 360w. Seasonic has a 300w that id probably go for.

[Hiitchy]

Take a look at this video from JayzTwoCents. It goes through power supplies, and what to look out for when buying one, and what the efficiencies mean in the long run.

 

[STRMfrmXMN]

8 minutes ago, NRST said:

I've heard that PSU efficiency is about 60 - 80% of it's load. What does that mean?

 

Planning to build a new pc for multimedia, after using pcpartpicker.com the TDP totals at 214w.

Should I take the 400w PSU or 450w?

 

Parts: https://pcpartpicker.com/user/NRST/saved/JJKzyc

(Is that how you link it?)

I hope any and all of these articles help. The first is a link to the pinned guide on our forum (PSU/Chassis subforum) about 80 PLUS efficiency 

 

[Enderman]

The efficiency range refers to at what load it is working at it's rated efficiency.

For example, if the PSU is 80+ gold between 60-80%, it will be slightly less efficient below 60% or above 80%.

That doesn't mean you can't use the PSU below or above that much %.

[stefanDB]

A 400W PSU will pull at max 400W from the wall, and at max load it will probably have around 80% efficiency, which means it can deliver around 320W to the system. that should be enough. it is always best to work with a comfortable margin, but this system won't use a lot of power.

[Froody129]

3 minutes ago, stefanDB said:

A 400W PSU will pull at max 400W from the wall, and at max load it will probably have around 80% efficiency, which means it can deliver around 320W to the system. that should be enough. it is always best to work with a comfortable margin, but this system won't use a lot of power.

Um no, AFAIK that 400w is what it can provide to the system, not what it's pulling from the wall. 

[stefanDB]

7 minutes ago, Froody129 said:

Um no, AFAIK that 400w is what it can provide to the system, not what it's pulling from the wall. 

I am sorry you are right, I read this somewhere but after further ivestigation it seems like I was wrong.

[bowrilla]

TL;DR

There are losses in every electrical component and the efficiency expresses that in a percentage. The more efficient the less losses.

 

Case study Corsair SF600

Have a look at the "Tech Specs" of this Corsair SF600 PSU (80+ Gold rating) for example.

 

The first chart shows you the efficiency curve of that specific PSU. It is lowest at no to low loads (85% – 86% efficiency depending on your power grid) and peaks between about 45% – 80% load (91% efficiency and better).

 

What does that mean?

Let's say your system needs about 70W at idle (as in running Windows Desktop and maybe having a browser open with very few tabs). Since this is a very low load for that specific PSU efficiency is low (~86%). That means that in order for your PSU delivering that 70W to your system it will drain more power from the wall. You can easily calculate it with this equation:

Psystem = Pwall * Efficiency

Bring efficiency to the other side and you'll end up with

Psystem / Efficiency = Pwall

In that given case your PSU will draw 70W / 0,86 = ~81,4W from the wall. At high system loads your system might need around 300W. That's pretty much 50% load on the PSU which equals to about 91% efficiency on 115VAC grids and about 92% on 230VAC ones. That means your system will draw about 300W / 0,91 =  ~329W – 326W from the wall.

 

What happends to the escessive Power?

One simple word: HEAT.

 

All electrical components (well, except super conductors being cooled down to almost absolute zero) have electrical resistance and as such they'll convert some electrical energy to heat. 

 

Why you should care

Unless energy is free of charge (as in: someone else is paying for it) more power equals to higher costs. And of course – 

heat. Sure, your PSU is by far not the hottest component in your system, but if heat is an issue in your room then aim for higher efficiency.

[NRST]

Thank you every one that helped  me regarding this.