# How to calculate max PSU output?

#### Lazar_99

##### Distinguished
So i'm a bit confused about how to calculate max 12V output. Most people say that 12V1@ 20A, 12V2@ 18A = 38 is wrong, some say otherwise. I don't really know but i want to calculate my PSU's max wattage output on all rails.
12V1@ 20A, 12V2@ 18A, +3.3V@ 26A, +5V@ 30A, -12V@ 0.5A, +5VSB@ 2.5A

#### WR2

##### Polypheme

What is the Max Combined +12V wattage for your PSU?

#### WR2

##### Polypheme
Usually, a calculation is not required. Most PSU data plates provide the information.

In this example the data plate says the 12V1 + 12V2 max load is 444W which is 37Amps.

#### smorizio

##### Titan

to get watt from a power supply you take the voltage times the amps..then add the wattage together.

240
216
85.8
150
6
12.5
the power supply should be stamp 700w-750w. if 100 load was used it would be 709w or so.
most vendor to be safe would rate the output of the ps for 80 percent of max voltage.
when you looking to put a high end video card into a system you have to see how the rails are wired in the power supply.
some have one large rail and some have more then one rail. if you have a ps with more then one rail hopfully they put each of the 6/8 pin pci power cable on two separate rails. as with your ps as long as the video card and the system power pull less then the max amp on one of the 12v rails you should be fine.

#### Rugger

##### Splendid
What is the make/model of your PSU? Look at the label on the side of the PSU and look for a maximum power rating for 12V1 and 12V2; it will look something like 'max combined output for 12V1 and 12V2 is 456W.' Tell us what the watts rating is for the max combined output. It's actually a simple calculation....divide the max combined by 12 and you have the max amps available on the 12V rails.

G

#### Guest

##### Guest

[strike]12V1@ 20A, 12V2@ 18A = 38 is correct[/strike]
[:lutfij:1]

#### Rugger

##### Splendid

It's not correct if the PSU mfr specifies a lower combined output capability; that is relatively common. You have to look at the ratings for the specific PSU in question.

#### WR2

##### Polypheme
Only if the MFRG rating for 12V1 +12V2 maximum combined wattage is 456W.

#### delluser1

##### Splendid

It's very seldom that the rails are additive
Happens even less often when talking about low quality power supplies like the OP's

No way of knowing how much power is actually allotted to the 12v

G

#### Guest

##### Guest

yeah and i have been up all night and realized that making a mistake like that means nighty nite.

thanks for correcting that

#### Lazar_99

##### Distinguished

but how can i figure out how much amps i have on both 12V rails together?

#### Lazar_99

##### Distinguished

That's exactly what i calculated. The result was 700 (i did that yesterday so i forgot but i know it was 700 and more) that's why i'm confused, it says on the box that its a 500W PSU. And if you mean by 80% vendor max voltage rate output, it also says on the box 80 plus bronze. lol

#### Lazar_99

##### Distinguished

oooh so that's what i needed to do LOL, to divide the max wattage output of the 12v rails. so by your theory i have 38 amps on the 12v rails. btw the maker is: Xilence and model is: XP500

#### Lazar_99

##### Distinguished

This one is ok, that's my PSU. I have it for 2 years now and it still works like new. Runs the R6850 and Phenom II X4 965 BE great/ I ran furmark to stress test my gpu thus check to see if my system is stable and it is. No problems with shutting down or lower performance.

#### Rugger

##### Splendid

You're welcome! I can definitely understand sleepy posts...Dell has caught me doing some too.

Lazar: You can't assume that your PSU can provide 38A on the 12V rail. As Dell pointed out, there is no way to tell what the max rating of your 12V rails is because the mfr doesn't state what the max wattage rating is for the 12V rails. It's not on the label or on the mfr's website. To me that is a big indication of a deceptive label and poor quality mfr. I highly doubt that it can provide 38A; the Seasonic S12II 520W provides 40A on the 12V rails and it is top tier PSU. For that PSU I would guess that the amps available on the 12V rails is closer to 30-32A at best.

I'm glad that your PSU is providing a stable power to your PC and you're not having any issues. That only thing that I would be concerned about is the quality of the power that it is providing. Lower quality PSUs are re-knowned for having poor voltage regulation and high ripple in their voltages; low-quality power causes pre-mature failure in components because the poor power damages PC components. I hope your system keeps running well - have a great day!

#### Lazar_99

##### Distinguished

Thanks and uhm the PSU has over voltage protection as well as short circuit protection and a few other features. it says maximum stability at all time, which i confirmed. and it says optimal performance in every situation and it also says that its approved by TÜV xDDD

#### ko888

##### Titan
Since the Xilence Redwing Series 500 R3 claims to meet ATX 2.3 power supply design specs that means the combined +12 Volt continuous current rating is 34 Amps.

The +12V values you see on the label are the peak current values not the continuous current values.