Are smaller PSUs better?

[jana519]

I'm planning on building a super power efficient PC for 1080p gaming - i3-6100, GTX 960, 1.2V RAM, and SSD. Peak power draw should be no more than 200W total, but average would be 150-175W.

Here's the PSU I'm looking at: http://www.newegg.com/Product/Product.aspx?Item=N82E16817151117&FM=1. 360W, Gold efficiency rated, SeaSonic unit. This gives me 160W headroom for theoretical power draw so it should operate close to 90% efficiency. But, as you may note, for the same price I can get a 500W-600W Bronze unit.

Other than price, is there any measurable benefit to choosing a smaller PSU more tailored to the specific components? And other than price, are there any measurable drawbacks to choosing a larger PSU with more than necessary headroom for specific componenrts?

I'm interested in your feedback before I make a final decision.

 

[aigomorla]

Well i heard theoretically PSU's are less efficient as they pull little to no load.

So an example would be like a 1kw PSU pulling 50W would not be as efficient as a psu raited at 200W pulling the same 50W load.

However if we look at math, were looking at at most 10W in a 50W load scenario...

While it may translate to being 20% more inefficient, the overall 10W on ones lighting bill, it would take 100h of activity to get 1Kwh which then translates to about ~ $.21 (depending on your location) for 100h... or $18.40 yearly if your PC is on 24/7 if you went with a larger psu which had a very bad efficiency.

 

[piasabird]

All power supplies have a power curve. In the sweet spot they provide power at the most efficient level with less fluctuation and produce less heat.

I know that some computers with no video cards only need about 60 watts of power so you need a power supply of around 150 to 200 watts because there may be times when there are more or less power requirements. If you operate at peak power all the time you may get a power surge during a thunderstorm or when the power goes out that can destroy your power supply. Even if a power supply is rated at 480 watts, that is a combination of all types of power it can create added up and put together. Each power rail has its own rating as well.

One thing to look out for is are there enough power plugs for things like SSD, Hard Drive, CPU P4, Main power, USB Keyboard and Mouse, Headset with earphones, possible digital Microphone, a Camera for Skype, changing cell phone.

I have been using this for a computer for watching TV on my 1040p 40" SAMSUNG HDTV:
http://www.newegg.com/Product/Product.aspx?item=N82E16817139026
It runs pretty quiet with My Z87N-Wifi Motherboard, + Hard drive +DDR3 + i3 Haswell build I dont do much gaming. Works fine for Youtube and HULU, Web surfing, E-Mail, etc.

 

[jana519]

Good points. So a larger 600W Bronze PSU would be only marginally less efficient (~10% less), but have substantially more headroom. Power savings would equal maybe $20/yr if the computer were on 24/7.

To me, that means if deciding between the 360W or the 600W at the same price point, efficiency rating would be negligible. 600W unit would allow for a GPU upgrade. However, if the SeaSonic unit uses Japanese made caps and has a 5 yr warranty, it would ultimately be more economical in the long run.

Do you agree with this?

 

[piasabird]

Here are some power suggestions I read online for a GTX 960:

http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-960/specifications

It recommends at least a 400w power supply.
Power usage for this model is 120w

You may find different video card models use more or less power.
This info is from a GEFORCE WEBSITE.
http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-960/specifications

 

[aigomorla]

Good points. So a larger 600W Bronze PSU would be only marginally less efficient (~10% less), but have substantially more headroom. Power savings would equal maybe $20/yr if the computer were on 24/7.

To me, that means if deciding between the 360W or the 600W at the same price point, efficiency rating would be negligible. 600W unit would allow for a GPU upgrade. However, if the SeaSonic unit uses Japanese made caps and has a 5 yr warranty, it would ultimately be more economical in the long run.

Do you agree with this?

yes i agree.

the 600W would give u a larger headroom incase you needed it.
The overall power savings in cost proabably would not even come out to 20 dollars / yr as it would probably only be at most 5-6% more inefficient.

 

[jana519]

Interesting. I wish more tech sites would include power supply power savings in their reviews. Moore's law is winding down and performance/watt is becoming just as relevant as raw performance now, so that could be a very useful metric.