Q: Power usage of PSUs?

[azel]

Let's say there is a 500W power supply unit.

Does it mean the maximum power it can supply to components is 500W?
Does it constantly use 500W and dissipate remaining energy as heat is the sum of components only requires 300W?

In other words I am wondering if replacing a PSU to a higher-powered one drives up the electricity bill when other components in the PC don't change.

Thanks!

 

[Fullmetal Chocobo]

If you have a 500w PSU, that is the maximum power that it can generate & provide to components. It might require more energy from the outlet to create that energy, depending upon the efficiency of the PSU. So if you have a PSU that is operating at 50% efficiency, and it is a 500w PSU, but it's only generating 400 watts for the components you have, then you are pulling 800 watts from the wall.

 

[pkme2]

Good Link for checkiing PSUs.
http://www.psuinquisitor.com/

 

[azel]

Ahh, so that's how it works.

Thanks Chocobo and pkme

 

[Howard]

It provides as much power as the components need. No more, no less. At least until maximum output is achieved.

 

[Ken90630]

Also keep in mind that not all 500W PSUs are created equal. Many PSUs have rated output capacities that were measured at 25 degrees Celsius, which is an unrealistic yardstick -- show me a high-power PSU that's only 25C inside under load and I'll sell you some beachfront property in Iraq. :laugh:

With said PSUs, the actual power output will be far less than 500W under "real world" conditions (temperatures). And if the PSU has poor efficiency, that means it'll run hotter and hotter as demand rises -- thus raising the temperature and thus lowering its power output capacity even further. Its fan should ramp up too and mitigate some of this, but heat is still likely to rise. You can see where this all goes.

Generally speaking, very few computers will ever draw much more than 200-250 watts, and that's at peak. Sometimes you need to buy a higher powered PSU in order to get sufficient amps on the 12V rail(s), but there aren't many rigs out there that really need a "500W" PSU. A Seasonic S12-430, as just one example, will run just about any computer out there. But for the ultra-high-end gamers running SLI or Crossfire or something, more power could be required. That's really what the 500- and 600-watt markets are for right now.

 

[NaOH]

Yeah...I have a 480w tagan (the max is higher from what I read) and it has a load controlled fan. The more components I use or install in my computer, the greater the load I put on the psu. I have a 3800x2, two hdd, 2 dvdrw, 1gb ram, wireless card, audigy 2 and 7800gt. No matter what I have done, I have never ever seen my psu load to the point where the fan is even blowing enough air for me to feel it come out of the case. That said, Ken90630 is correct in saying that 500w and beyond is for SLi and the such. You never want to run your psu at it's maximum load capacity all the time either since it will die faster, hence the need to upgrade to a psu that produces more power.

 

[Jiggz]

So the answer to the OP is NO but not really NO! Upgrading to a higher wattage PSU without a change in load will not change your electric bill, virtually. There will be a minute increase but that's just a "chunk of change". This is caused by a bigger transformer in the higher wattage PSU which requires a higher excitation current to maintain proper output. But a PSU will only provide power required by the load up to it's limits or ratings. Most PSU works at best efficiency between 35-70 percent loading.