Do 1000W PSU's ALWAYS use that power?

[Pulsedriver]

Hey folks,

So I was thinking... Say you buy a 1000W PSU but your system components are only drawing 500W, does the PSU run at a continious 1000W?

Surely if they did, it would mean massive electricity bills?

Just a thought...

 

[Werewolf]

PSU's should only draw a bit more power than they need at that time, so a 1000w PSU should only draw a bit more than 200watt* at the mains if that is all the system needs at that time.


*Say the PSU is 80% efficient, then it would pull about 240watt from the wall.

 

[Pulsedriver]

Is that expensive to run?

 

[BillytheImpaler]

No, it isn't. Modern PSUs are switching which, as above, means that they only draw as much power as is being required from them. If, as in your example, your rig was only using 500W from a 1kW PSU it would only draw 500W (actually slightly more since no PSU is 100% efficient). If your rig draws 500W it won't cost too much more to run a 1kW PSU over a 550W one. Typically good quality PSUs get more efficient as they approach their design load.

 

[eyetrip]

Which brings up a question (sorry for the hijack), but what is the most efficient PSU?

I was wondering about this the other day... might be tempted to get one, whatever it is

 

[topshot]

most decent spec PSU's are 80-90% efficient, Corsair, Seasonic, Enermax etc all fall in to the 80%+ bracket.

Cheap PSU's tend to be very inefficient especially as they age

 

[Admiral Huddy]

No, it isn't. Modern PSUs are switching which, as above, means that they only draw as much power as is being required from them. If, as in your example, your rig was only using 500W from a 1kW PSU it would only draw 500W (actually slightly more since no PSU is 100% efficient). If your rig draws 500W it won't cost too much more to run a 1kW PSU over a 550W one. Typically good quality PSUs get more efficient as they approach their design load.

Good post and this is the reason why it's best to get a PSU which is rated slightly higher than the draw of your components. Not only does this provide greater stability, but allows some headroom for future upgrades.

 

[pegasus1]

Contrary to what the PSU companies tell us, you dont need an Uber 1Kw PSU to power a decent rig. Having said that not all 500W PSU's are created equal.

 

[LeoPheonix]

It is also worth considering that if you buy a psu now you want it to last through your next upgrade(s). with that in mind it may not be long before 1kw is overkill. However you still risk incompatible connectors and the possibilty of being tempted by something else new and shiney later on

 

[pegasus1]

It is also worth considering that if you buy a psu now you want it to last through your next upgrade(s). with that in mind it may not be long before 1kw is overkill. However you still risk incompatible connectors and the possibilty of being tempted by something else new and shiney later on

True, im not a great individual part upgrader, id rather upgrade the whole machine normally 12-18 months at a time. Its easier to ensure compatability and getting components that complement each other.

 

[sunama]

It is also worth considering that if you buy a psu now you want it to last through your next upgrade(s). with that in mind it may not be long before 1kw is overkill.

Sorry man, but a 1kw psu is way over the top. As time progresses computer component makers are moving towards higher efficiency. We have already seen Intel do this with their move from the Prescott to the C2D cpus. The more efficient, the better. Even hard disk makers are moving towards lower power usage (Western Digital and marketing their drives with this in mind). PSUs (as has been discussed in this thread) are getting more efficient and I think this trend will continue.

The only time you would ever need 1000W psu is if you have perhaps 3 video cards run in SLI (if thats possible) and 10 hard disks, with an overclocked inefficient cpu (which they dont make anymore) all running simultaneously.

I cant even think of a system that would require anything more than a 620w psu, right now. Even running a quad cpu and 2 8800GTXs, all overclocked wouldnt bring a 620w to its knees.

Consider that companies such as DELL (which dwarf enthusiast PC sales) are happy to use 425W psus for their 8800GTX equipped systems and you can guarantee that it will be a cheap PSU. They do have a system that uses a 1000w psu, but only a single model uses this.