PSU efficiency truth

[eezolive]

So guys

I pretty much what to know your opinions/facts on PSU efficientsy

For me the big mystery is

is having a low watt PSU more energy efficient????????

my gut feeling is NO. its like saying a small tank means the car is more fuel efficient.
If you think of your PSU as your pc's juice tank... you have to wonder how much does power rating affect consumption rate???

Whats the truth?

 

[el3venth]

The truth is that no PSU is efficient at all loads. They all reach a peak efficiency at a certain load.
So it all depends on the load.

Power Supply Fundamentals | silentpcreview.com

 

[JollyJamma]

I had someone tell me that lighter PSUs are better than heavier PSUs because they do the same with less Trolololol he was.

 

[jasong]

A psu should be certified for continuous peak efficiency at its stated voltage.

 

[Senshi]

The truth is that no PSU is efficient at all loads. They all reach a peak efficiency at a certain load.
So it all depends on the load.

Power Supply Fundamentals | silentpcreview.com

Good link, but a bit outdated.

Generally speaking more efficient power supplies = use less power from the wall = cheaper.

http://en.wikipedia.org/wiki/Power_supply_unit_(computer)
80 PLUS - Wikipedia, the free encyclopedia
http://www.dailytech.com/New+80+PLU...fficiency+Target+Datacenters/article16955.htm

Gold rating is usually the best (and most expensive).

 

[eezolive]

I have set up a download rig, purposely using a low 35 watt cpu (pentium G260T). the plan is to run it 24/7 at lowest running cost (electricity consuption wise).
I have a spare Gigabyte PoweRock EX 400W in there.

Will it be better consumption wise to put a 150watt PSU? Or should i stick to the 400W because it just may be more efficient than a 150Watt at low load?

 

[Senshi]

I have set up a download rig, purposely using a low 35 watt cpu (pentium G260T). the plan is to run it 24/7 at lowest running cost (electricity consuption wise).
I have a spare Gigabyte PoweRock EX 400W in there.

Will it be better consumption wise to put a 150watt PSU? Or should i stick to the 400W because it just may be more efficient than a 150Watt at low load?

The wattage rating of the psu has got nothing to do with how much power the PSU consumes to provide the required wattage.

Let's say the PC needs 100w of power, if you have an 80% efficient PSU, it will need 125W worth of power from the wall.

To put it mathematically 125x0.8 = 100. The formula to work out how much power you need for a wattage is Wattage divided by efficiency = power draw.

Therefore the higher the efficiency of the psu, the less power it needs to draw from the wall to provide the required power for the system. This is where the ratings come in on the PSU's, hence Gold rated is usually the best.

Unfortunately as far as my knowledge goes, you don't really get Gold rated PSU's under 400W. I would settle for a silver or bronze rated PSU in that range instead.

 

[Mandarin]

Go for Gold rating... If a PSU is marked as a 850W it does not mean you will get the full 850.. The High Current Pro's of Antec are the bomb! You won't go wrong..

 

[eezolive]

thanx slick... that answers it

 

[Oj0]

Yes and no. PSUs are highly inefficient at low loads, so for example you have a system drawing 300w and two PSUs:

1. 1200w, 85% efficient
2. 400w, 80% efficient

You may find that the 1200w is only 40% efficient at 300w, while the 400w is 75% efficient at the same load. Have a look at JonnyGuru's charts for his PSU stability tests, at a VERY low wattage (less than 10w) many of your massive PSUs drop to efficiencies as as 20% or lower. It will vary from PSU to PSU and, as the rating given is only at a high load, there is no way to find out without using something like a Kill-A-Watt.

 

[Senshi]

Yes and no. PSUs are highly inefficient at low loads, so for example you have a system drawing 300w and two PSUs:

1. 1200w, 85% efficient
2. 400w, 80% efficient

You may find that the 1200w is only 40% efficient at 300w, while the 400w is 75% efficient at the same load. Have a look at JonnyGuru's charts for his PSU stability tests, at a VERY low wattage (less than 10w) many of your massive PSUs drop to efficiencies as as 20% or lower. It will vary from PSU to PSU and, as the rating given is only at a high load, there is no way to find out without using something like a Kill-A-Watt.

Some PSU's do have a efficiency rating at a certain load percentage (say 40% efficient at 0-300W or 40% psu usage). But Basically it comes down to what you are powering. To be honest, for what you are running any decent name brand 400w+- Bronze psu should be efficient enough.

 

[Oj0]

It's also not worth spending R1k on a PSU to save R20/year on electricity... Just keep that in mind. The savings won't be worth the effort involved in replacing the PSU.

 

[eezolive]

Thanx guys.. Excellent info!