Question How do i calculate how strong my psu needs to be?

[Allen_22]

Graphic cards have certain requirements, but, i assume so do other components. Do i use the sum of these requirements?

 

[MeanMachine41]

Hi Allen

I just calculate the max TDP of each hardware component then add 20% for safety and expansion. More accurate than generic PSU calculators.
Also it's not just strength (in terms of Wattage) you should consider but quality and most importantly Efficiency.
The PSU is the lifeblood of your system and should not be underestimated. Read my PSU fact sheet.

 

[Allen_22]

Hi Allen

I just calculate the max TDP of each hardware component then add 20% for safety and expansion. More accurate than generic PSU calculators.
Also it's not just strength (in terms of Wattage) you should consider but quality and most importantly Efficiency.
The PSU is the lifeblood of your system and should not be underestimated. Read my PSU fact sheet.

Yes i'm aware that the quality of the psu is very important, however until recently i used psus whose wattage was just the one needed by the gpu. Did i do someting wrong?

 

[MeanMachine41]

Yes you have assumed incorrectly? What do you think would have supplied power to the rest of your components?
The PSU provides power to 12V, 5V and 3volt rails. The GPU operates/receives power from the 12V rail.

 

[Allen_22]

Yes you have assumed incorrectly? What do you think would have supplied power to the rest of your components?
The PSU provides power to 12V, 5V and 3volt rails. The GPU operates/receives power from the 12V rail.

so if a gpu says it needs 500 watt how much stronger does my psu actually need to be?

 

[MeanMachine41]

so if a gpu says it needs 500 watt how much stronger does my psu actually need to be?

As I said, You calculate the MAX TDP draw of each hardware component in your whole system then add 20%.
If you want a PSU recommendation then list your system specs.

 

[Karadjgne]

http://www.realhardtechx.com/index_archivos/Page362.htm

What it says here is a rough cumulative total. For instance, a 750ti is only a 75w draw, but asks for a minimum of 400w psu. That covers 4 things. The cpu, the gpu, the rest of the pc and an averaging of quality. You could use a junky 400w psu, a good quality 350w etc.

 

[Wolfshadw]

The recommendations you find on graphic card sites are for the entire system. So if a site says recommended 500 watts, that's for the entire system; not just the graphics card. No graphics card on the market will use more than 375 watts (75w PCIe Expansion Slot + 150w 6+2PCIe power_1 + 6+2PCIe power_2).

-Wolf sends

 

[hotaru251]

EVGA - Power Meter

EVGA is here to help you find the right EVGA Power Supply for your system. Please fill out the following information, and we will offer our suggestions to you.

www.evga.com

can adjust gpu/chipset/cpu if its OC or not, how many drives(both hdd and ssd) and more and it'll give a decent estimate of how large of one you should use.


dont have to buy their brand (just use it to figureo ut the pwoer needed and buy that from w/e brand you favor.)

 

[Allen_22]

The recommendations you find on graphic card sites are for the entire system. So if a site says recommended 500 watts, that's for the entire system; not just the graphics card. No graphics card on the market will use more than 375 watts (75w PCIe Expansion Slot + 150w 6+2PCIe power_1 + 6+2PCIe power_2).

-Wolf sends

In that case i'm assuming that companies tend to overstate psu requirements? saying 450 instead of 400.. just in case someone with a 10 dollars worth 400 psu fries their card...

 

[Karadjgne]

Yes and no. Seasonic, Delta and a couple of others have built designs that over spec, mostly it depends on the vendor as to which unit does. Just about any HP or Dell OEM supply built by those 2 OEMs is over spec'd. But you'll find that most units are not, sometimes by a long shot.

It's mostly a matter of quality. Not just quality of build, but quality of components. When you start using the cheapest, low grade capacitors in important areas that take a lot of abuse electrically, use low grade or barely effective coils or a cheap and ineffective platform with no real protective circuitry, slap a 500w sticker on it, I'd not expect it to hold that 500w or anything close, before burning out. On the other hand, you can take a very good quality unit at 450w and push it to 400w demand, and it'll do that for years without worry.

Most cheapo companies fib when it comes to size. They don't take a realistic approach. They'll include a large amount of the 3.3 and 5v+ rails and add that into the total.

 

[Wolfshadw]

In that case i'm assuming that companies tend to overstate psu requirements? saying 450 instead of 400.. just in case someone with a 10 dollars worth 400 psu fries their card...

Yes. Graphic card companies do overstate power supply recommendations. They do so, so they do not get bit in the rear when someone says, "But your site said I only needed..."

What I do is look at what power connectors the graphics card has.

The PCI-Ex16 expansion slot provides up to 75 watts of power.
The 6-pin PCIE power cable provides up to 75 watts of power.
The 6+2-pin PCIE power cable provides up to 150 watts of power.

If a graphics card has no PCIE power ports, then even at full load, it will never require more than 75 watts of power. (While I wouldn't need nearly this much, I don't go with less than 400 watts)
If a graphics card has a single 6-pin PCIE power port, then at full load, it will never require more than 150 watts of power. (I'd get a quality 450 watt PSU)
If a graphics card has two 6-pin PCIE power ports, then at full load, it will never require more than 225 watts of power. (I'd get a quality 500 watt PSU)
One 6-pin and one 8-pin? 300 watts of power. (I'd get a quality 550 watt PSU)
Two 8-pins? 375 watts of power. (I'd get a quality 600 watt PSU)

If you're building a system and you don't know what graphics card you're going to get or it's power requirements, there's no reason (save budget) not to get a quality 600 watt power supply. Brands that I trust include:
Antec
FSP Group
PC Power and Cooling
Seasonic (currently running Focus Gold 550)
Super Flower

-Wolf sends