Is having an overkill PSU bad?

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Billspear

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Sep 26, 2014
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My current PC that I'm planning to order has an estimated power wattage usage of 127W. You can view it here:

LINK TO BUILD (I was originally planning on getting the 550W version of that PSU but they literally just sold out as I was about to order :( What are the chances?)

So my question: does going overkill on a power supply warrant any concern? Are there any possible problems such as stability issues?

I'm considering to possibly upgrade to an i7-4790k with a GTX 960 (when available) in the future. Just a thought at this point and not 100% sure.
 
Solution
Vexillarius
A PSU's efficiency is the ratio between the amount power it delivers to the components and the amount of power it draws from the wall socket.

For example, a PSU with an efficiency of 80% that has to deliver 400 watts to a PC will draw 400w / 0.80 = 500w from the wall.
A PSU with an efficiency of 92% that has to deliver 400 watts will draw 400w / 0.92 = ~435w from the wall.
The amount of power that is ultimately delivered to your PC is the same regardless of efficiency, the only thing that is affected by it is the amount of power that's drawn from the wall. The lost power is translated into heat.
Efficiency will go up and drop because of temperature and load (a few percentage points, nothing to worry about), but it is mostly affected by...
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Vexillarius

Vexillarius

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Most PSU's are a little bit less efficient at very low loads, but the effect is minor enough to not warrant concern, it's a few percent at most.

On the other hand, a PSU that isn't stressed much is usually quieter than a very stressed PSU, and it will usually also last longer.

I wouldn't worry about it at all, you got a great PSU that will work absolutely fine for your system, and then some.
 
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Billspear

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What exactly do you mean by it will be less efficient? If it's overkill, it wouldn't effect anything negatively or bother with stability? And is the effect on efficiency only temporary? Sorry, I'm just trying to understand.

Also, I believe that that XFX XTR power supply incorporates hybrid-fan technology which allows you to select whether the fan stays on or off depending on temperature and load. Will this ultimately help with the life-span of the PSU? I will be operating at such a low load and temp for the time being.

 
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Vexillarius

Vexillarius

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Aug 23, 2014
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A PSU's efficiency is the ratio between the amount power it delivers to the components and the amount of power it draws from the wall socket.

For example, a PSU with an efficiency of 80% that has to deliver 400 watts to a PC will draw 400w / 0.80 = 500w from the wall.
A PSU with an efficiency of 92% that has to deliver 400 watts will draw 400w / 0.92 = ~435w from the wall.
The amount of power that is ultimately delivered to your PC is the same regardless of efficiency, the only thing that is affected by it is the amount of power that's drawn from the wall. The lost power is translated into heat.
Efficiency will go up and drop because of temperature and load (a few percentage points, nothing to worry about), but it is mostly affected by the quality of the PSU. 80Plus is a certification given to PSUs that are proven to have a certain effiency.

Also, for example a 550w PSU will only deliver as much power as is needed at that point in time. The maximum is 550w, if your PC at a certain point only uses 130w then the PSU will draw '130w / efficiency' from the wall and it will deliver 130w to the PC.

In the end it doesn't noticably matter for system stability if you only draw a low load from the PSU, it's nothing to worry about. At low loads like this there also wouldn't be a noticable effect on lifespan if you put the PSU on semi-fanless or normal mode. I'd say turn on the hybrid-fan mode and enjoy the silence ;)
 
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Billspear

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THANK YOU SO MUCH! That answers all of my power supply efficiency questions in great detail and clarity. I think I'll go with that XFX.

And I certainly will be enjoying that quiet hybrid-fan mode! It will be paired with Fractals R4 silent sound-dampening case :D
 
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