Good deal for a 750W PSU?

[NukaCola]

http://www.zipzoomfly.com/jsp/...p?ProductCode=10006237

I'm thinking of upgrading my computer (actually, a totally big makeover -- new GPU, new mobo, new CPU, new RAM, new PSU) within 6 months, and seeing as how I'll probably upgrade to something like a 8800GT and a dual-core processor, will 750W be enough? My current PSU is 520W, and it's an OCZ Powerstream.

 

[MarcVenice]

It's a good powersupply, but your current PSU might be able to handle your rig just fine. Not long ago you could actually get that 850w version for 80$ !!! But for 120$, hmz, you might want to consider a 520/620hx instead, because it's modular, which is really a plus if you ask me. 520hx should in fact, for 90$ or so, be able to handle anything you buy just fine.

 

[NukaCola]

sorry, what does the hx mean?

 

[MarcVenice]

Oh, sorry, I ment the Corsair 520hx/620hx, it's one of their PSU's, with modular cables, very stable, qaulity PSU's. http://www.newegg.com/Product/...E16817139001&Tpk=520hx 750w is nice, but it's overkill for most rigs, unless you are running dual high-end videocards and a overclocked qaud, watercooled and what not.

 

[imported_Scoop]

For the love of god you don't need a 750W PSU for that, are you serious? The only thing it's good for is giving a bigger number on your electricity bill. You're fine with your current PSU.

 

[John]

Originally posted by: Scoop
For the love of god you don't need a 750W PSU for that, are you serious? The only thing it's good for is giving a bigger number on your electricity bill. You're fine with your current PSU.

Actually that is a misconception. A 300W load on a psu is the same no matter what the wattage rating of the psu listed as. It's the efficiency of the psu that plays a vital role on the amount power that is required from the wall socket. That 200W load on a 300W psu that is only 70% efficient will require 429W from the wall, and if the 750W is 80% efficient it will only require 375W. Therefore in this case the higher wattage psu saves you money on your electric bill.

1000(kWhr)/54(wattage difference)*.15(cents per kWhr)*24(hours)*365(year)=$70.96 (yearly savings)

 

[DSF]

Originally posted by: John

Originally posted by: Scoop
For the love of god you don't need a 750W PSU for that, are you serious? The only thing it's good for is giving a bigger number on your electricity bill. You're fine with your current PSU.

Actually that is a misconception. A 300W load on a psu is the same no matter what the wattage rating of the psu listed as. It's the efficiency of the psu that plays a vital role on the amount power that is required from the wall socket. That 200W load on a 300W psu that is only 70% efficient will require 429W from the wall, and if the 750W is 80% efficient it will only require 375W. Therefore in this case the higher wattage psu saves you money on your electric bill.

1000(kWhr)/54(wattage difference)*.15(cents per kWhr)*24(hours)*365(year)=$70.96 (yearly savings)

What math are you doing to calculate the wattage pulled from the wall?

By my understanding, a 70% efficient PSU transfers 70% of the power from the wall into usable juice for the PC. So to figure out how much wattage a 70% efficient PSU needs from the wall to supply 200W to the PC, we use this equation:

.7(x) = 200W

Dividing both sides by .7, we get that x, the power from the wall, equals ~285W.

For the PSU that's 80% efficient, we start with this:

.8(x) = 200W

and find x to be 250W.

There's still a difference, but it's smaller than you made it out to be. I'm wondering where you came up with 429 and 375.

Regardless, this has nothing to do with the size of the power supply, only its efficiency. Also, my understanding is that some PSUs are less efficient if they're running below half of their maximum load, which may make it less cost-effective to run a larger PSU. (This depends, however, on the particular unit's efficiency curve.)

As far as the original post, a modern computer with a dual-core processor and an 8800GT draws at most something in the neighborhood of 200-250W from the wall at full load. A quality 400W PSU is plenty to power your upgrades. Your old PSU is probably sufficient, assuming it can supply the necessary amperage on its 12V rail(s). If it can supply more than 25A using some combination of the +12V rails, you should be fine.

 

[jonnyGURU]

Originally posted by: DSF

Originally posted by: John

Originally posted by: Scoop
For the love of god you don't need a 750W PSU for that, are you serious? The only thing it's good for is giving a bigger number on your electricity bill. You're fine with your current PSU.

Actually that is a misconception. A 300W load on a psu is the same no matter what the wattage rating of the psu listed as. It's the efficiency of the psu that plays a vital role on the amount power that is required from the wall socket. That 200W load on a 300W psu that is only 70% efficient will require 429W from the wall, and if the 750W is 80% efficient it will only require 375W. Therefore in this case the higher wattage psu saves you money on your electric bill.

1000(kWhr)/54(wattage difference)*.15(cents per kWhr)*24(hours)*365(year)=$70.96 (yearly savings)

What math are you doing to calculate the wattage pulled from the wall?

By my understanding, a 70% efficient PSU transfers 70% of the power from the wall into usable juice for the PC. So to figure out how much wattage a 70% efficient PSU needs from the wall to supply 200W to the PC, we use this equation:

.7(x) = 200W

Dividing both sides by .7, we get that x, the power from the wall, equals ~285W.

For the PSU that's 80% efficient, we start with this:

.8(x) = 200W

and find x to be 250W.

There's still a difference, but it's smaller than you made it out to be. I'm wondering where you came up with 429 and 375.

Your math is correct. John might be a bit tired tonight.

But the point that John makes does remain, and since the older Powerstream 520W is less efficient than the more current Cooler Master 750W, it would actually be cheaper to run the Cooler Master than the Powerstream.

Unfortunately, it'll take about 10 years of 24/7 use for you to save enough to pay for the PSU.

So keep the existing PSU, and if problems crop up because of not enough power on the +12V or the age of the unit, etc. THEN replace it. Don't replace it simply because you THINK you need a bigger PSU. An 8800GT can run on a good 500W. SLI on a good 550W.

 

[John]

Originally posted by: DSF
There's still a difference, but it's smaller than you made it out to be. I'm wondering where you came up with 429 and 375.

I failed to proof my reply, and the 200W should read 300W.

300/.7=429
300/.8=375

Regardless, this has nothing to do with the size of the power supply, only its efficiency.

I stated that as well.

 

[rickkipp]

:thumbsup: Newegg has a good deal on the OCZ GameExtreme 700 watt psu now: $105.00! Great ratings, great brand:

http://www.newegg.com/Product/...x?Item=N82E16817341002

 

[imported_Scoop]

Actually the point I was trying to make was that with a 750W PSU that system runs at around 170W idle resulting in a ~23% load for the most time. Can you actually seriously in all honesty say that a PSU is at it's most efficient at 23% load? Where as the 520W PSU would be running mostly at ~33% load which is a whole lot better. Of course I don't know excatly what kind of efficiencies these two units have at that level, so if the OCZ PSU is a total POS then my bad.

 

[DSF]

Originally posted by: John

Originally posted by: DSF
There's still a difference, but it's smaller than you made it out to be. I'm wondering where you came up with 429 and 375.

I failed to proof my reply, and the 200W should read 300W.

300/.7=429
300/.8=375

Regardless, this has nothing to do with the size of the power supply, only its efficiency.

I stated that as well.

Must have missed it. Cheers.

 

[jonnyGURU]

Originally posted by: Scoop
Actually the point I was trying to make was that with a 750W PSU that system runs at around 170W idle resulting in a ~23% load for the most time. Can you actually seriously in all honesty say that a PSU is at it's most efficient at 23% load? Where as the 520W PSU would be running mostly at ~33% load which is a whole lot better. Of course I don't know excatly what kind of efficiencies these two units have at that level, so if the OCZ PSU is a total POS then my bad.

I wouldn't say that the OCZ is a total POS. It's just "old school" by today's standards where 80%+ efficiency wasn't such a concern.

The OCZ never gets to 80% efficiency, so I don't care what the OP's load actually is. The Cooler Master IS 80% efficient, even at only 20% load.

 

[sixsixeight]

Don't know if you've bought a PSU yet or not, but, Buy.com has the Corsair TX750W for $100 after $45 rebate. Seems like the general consensus is that you don't need a PSU this powerful, but, if you're going to spend that amount of money, might as well get one with some headroom.

 

[mageslayer]

I second the corsair tx750w. It's a great psu with plenty of headroom for future upgrades.

 

[Zap]

Check the Hot Deals forum... I think the Cooler Master 750W PSU is available for around $50 after a $50 rebate.