PSU output vs draw.

[Jakers038]

One, or maybe even several, websites from my country (Serbia) have "effective power" (i'll shorten it to EP) written in characteristics of PSU's and this EP is always less by some 80-ish percent than what the PSU has in it's name, for example in the case of a Raidmax 500XT, a 500W PSU, it says that it has a EP of just 400W.

 

On the other hand, I've heard somewhere that you don't get less Watts by having a smaller efficiency, but instead you get for example 500W as you should, but more, for example 600W, is drawn from the wall.

 

So is that "effective power" just something a noob marketer made up or do you really need to get more than a 500W psu if you want to achieve solid 400 or 450W?

[Cereal5]

Any good PSU will put out the wattage it is rated for. Efficiency determines how many MORE watts it has to draw in order to send that much to your computer. I've never heard of an "effective power" before, but I'd stay away from it.

[Spotty]

18 minutes ago, Jakers038 said:

On the other hand, I've heard somewhere that you don't get less Watts by having a smaller efficiency, but instead you get for example 500W as you should, but more, for example 600W, is drawn from the wall.

This... Assuming that the PSU is halfway decent and not just lying about its ratings.

 

19 minutes ago, Jakers038 said:

One, or maybe even several, websites from my country (Serbia) have "effective power" (i'll shorten it to EP) written in characteristics of PSU's and this EP is always less by some 80-ish percent than what the PSU has in it's name, for example in the case of a Raidmax 500XT, a 500W PSU, it says that it has a EP of just 400W.

It has 430W on the 12V rail, and another 110W on the 5V & 3V rails (according to its spec sheet). The "effective power" rating you saw may have been referencing the 12V rail. Total power output is listed as 500W.

 

[Jakers038]

I guess that whoever is in charge of marketing there has no idea what they're doing then, because to be honest, for someone who has no idea how PSU's work, it would make logical sense that efficiency determines how much W you get out of the total W the PSU is supposed to give.

[OrionFOTL]

Please post some links to the stores that do that. It sounds absolutely hilarious.

[Stefan Payne]

21 hours ago, Jakers038 said:

One, or maybe even several, websites from my country (Serbia) have "effective power" (i'll shorten it to EP) written in characteristics of PSU's and this EP is always less by some 80-ish percent than what the PSU has in it's name, for example in the case of a Raidmax 500XT, a 500W PSU, it says that it has a EP of just 400W.

That sounds like utter horseshit.

Because the Efficiency means the Power Loss, not the Loss of Power to the Components...

It could make sense with some low quality units but not for good named brand ones...

[Guest]

On 11/8/2018 at 12:27 AM, Jakers038 said:

One, or maybe even several, websites from my country (Serbia) have "effective power" (i'll shorten it to EP) written in characteristics of PSU's and this EP is always less by some 80-ish percent than what the PSU has in it's name, for example in the case of a Raidmax 500XT, a 500W PSU, it says that it has a EP of just 400W.

 

On the other hand, I've heard somewhere that you don't get less Watts by having a smaller efficiency, but instead you get for example 500W as you should, but more, for example 600W, is drawn from the wall.

 

So is that "effective power" just something a noob marketer made up or do you really need to get more than a 500W psu if you want to achieve solid 400 or 450W?

Ok.. As others have said... That's just shit.

 

The PSU is shit, that is.

 

"Effective power" is the continuous output power.  What they're selling it as is "peak power".  This has nothing to do with input vs. output power.

 

So take your Raidmax example....

 

It's sold as a 500W.  But that's 500W peak.  Meaning it may be able to put out 500W for 10ms at 25°C temperature.  What it can actually output continuously is 400W.

 

General rule of thumb:  ANY power supply that's sold at "peak power" and has a listed "effective" or "continuous" output listed separately should be avoided.  They're probably bad quality, but also probably just a poor value.  They have to trick customers and call it a "500W" to be competitive with actual 500W PSUs on the market.

 

[OrionFOTL]

58 minutes ago, jonnyGURU said:

So take your Raidmax example....

 

It's sold as a 500W.  But that's 500W peak.  Meaning it may be able to put out 500W for 10ms at 25°C temperature.  What it can actually output continuously is 400W.

Raidmax RX-500XT is rated 500W at continuous power, though. It doesn't list it as peak power, and doesn't list peak power separately either. The store must really do some funny calculations themselves, based on incorrect understanding of efficiency or whatever sorcery they use.

[17030644]

On 11/8/2018 at 2:27 AM, Jakers038 said:

One, or maybe even several, websites from my country (Serbia) have "effective power" (i'll shorten it to EP) written in characteristics of PSU's and this EP is always less by some 80-ish percent than what the PSU has in it's name, for example in the case of a Raidmax 500XT, a 500W PSU, it says that it has a EP of just 400W.

 

On the other hand, I've heard somewhere that you don't get less Watts by having a smaller efficiency, but instead you get for example 500W as you should, but more, for example 600W, is drawn from the wall.

 

So is that "effective power" just something a noob marketer made up or do you really need to get more than a 500W psu if you want to achieve solid 400 or 450W?

THE SECOND POST ON TOP OF THE PSU SECTION EXPLAINS IT VERY WELL

 

 

- "If you have a 1000W PSU with an 80% efficiency then you are only going to be able to get 800W from your power supply." This is incorrect. If you have an 80% efficient 1000W PSU then, when putting it under enough load to max its output you are going to be drawing more power from the walls - not losing output from your power supply. In this instance, putting a 1000W PSU under max load with an 80% efficiency would mean you're drawing 1250 watts from the wall. Math goes as such:
                                                                                                X / Y= Z                  
                                                                                        1000W / .80 = 1250

                                                                                  1250W drawn from the wall

X represents the wattage you're using (say 350W with a Ryzen 5 1500X and GTX 1080 Ti under 100% system load), Y represents the efficiency in decimals (an 85% efficient PSU would be .85), and Z represents your total system draw from the wall. For this calculation we're assuming that the PSU in question has exactly enough wattage to power the system at 100% load and is 87% efficient at 100% draw, making it an 80+ Gold efficient power supply.


So in our case with the 1500X and 1080 Ti:

                                                                                               350 / .87

                                                                      = 402 watts drawn from your power outlet

 

Note, however, that efficiency is not consistent throughout the load of the power supply.

Power supplies are more and less efficient at different loads. They are also more efficient when connected to a more powerful grid, the 230V nominal, which you may use if you don't live in North America. Check that your PSU allows for operation under both voltages. Most modern ones switch operation automatically. Other, often older units, will have a hard switch at the back of the unit to switch to choose from either 115V or 230V (note, DO NOT SWITCH TO THE ONE THAT DOESN'T MATCH THE ELECTRICAL OUTPUT OF YOUR WALL OUTLET! This doesn't usually end well!). This graph demonstrates the efficiency curve of a Corsair TX750 when plugged into a 115V AC versus being plugged into a 230V AC. Note the TX750 is an 80+ Bronze rated PSU.
                

                                      

 

If you live in the United States, for example, you are using a 110-120V (115 nominal) AC through a standard NEMA 5-15 socket. Your power supply may be more or less efficient than your manufacturer claims because they may advertise efficiency through a 230V AC, though standard 80 PLUS efficiency testing is done on a 115V AC. Note that these tests for efficiency are also done under very specific test environments and do not necessarily reflect real-world scenarios so you may achieve higher or lower efficiency than rated by the manufacturer.

And just to finish up let's go list the various 80 PLUS ratings and their efficiency at different power draws on a 115V and 230V AC as well as 230V AC redundant.

THIS IS THE POST

 

 

 

[Guest]

23 hours ago, OrionFOTL said:

Raidmax RX-500XT is rated 500W at continuous power, though. It doesn't list it as peak power, and doesn't list peak power separately either. The store must really do some funny calculations themselves, based on incorrect understanding of efficiency or whatever sorcery they use.

Ah...  I assumed it was rated at peak because:

 

1.  It's Raidmax.  I mean... come on.... Riadmax?

 

2. Usually when a company gives peak over continuous, it's 100W delta.