a 500w PSU, that's "80 Plus", will draw 650w from the plug?

[swapjim]

I'm trying to understand something.

Lets say I have a 500w PSU that's 80 Plus. And for the shake of this example, lets say that it's efficiency is exactly 80%.

Does that mean that:

A. the PSU delivers 500w inside my computer but draws (consumes) 650w from the plug? Or:
B. the PSU delivers 400w inside my computer and draws (consumes) 500w from the plug?

 

[bononos]

Yes you're right, the psu will draw more from wall socket because of conversion (in)efficiency. 500W is the maximum though and pc's will typically draw alot less unless you have power hungry equipment.

 

[dave_the_nerd]

Yeah, basically. But the actual efficient number varies depending on the load.

Different certifications (80+, 80+ Bronze, 80+ Gold, etc.) have different curves.

https://en.wikipedia.org/wiki/80_Plus

 

[Justinus]

AFAIK the answer is B.

Your psu will deliver 500 watts to your PC, which at an efficiency rating of 80% would draw 625 watts from the wall.

 

[lehtv]

AFAIK the answer is B.

No, the answer is A. A 500W unit is rated for 500W worth of output (DC) power. If the answer was B, then a given rated wattage would result in different maximum output power for different efficiency ratings, which would make no sense at all.

It should be noted that a 500W rated unit should never be paired with components that actually require 500W of power. The rated wattage is your ceiling and you should always try to stay well below it so as not to squeeze life out of the unit prematurely. Power supplies will also run unnecessarily loud and hot when near their maximum wattage.

 

[swapjim]

No, the answer is A.

Yes, that's what he meant. He elaborates in the next line:

Your psu will deliver 500 watts to your PC, which at an efficiency rating of 80% would draw 625 watts from the wall.

It should be noted that a 500W rated unit should never be paired with components that actually require 500W of power. The rated wattage is your ceiling and you should always try to stay well below it so as not to squeeze life out of the unit prematurely. Power supplies will also run unnecessarily loud and hot when near their maximum wattage.

I'm calculating my wattage right now. I'm going to open a thread just for that.

I see a concesus for B, so B it is then!

Thanks everyone!

 

[Justinus]

Yes, I meant A. Mobile forums browsing ftl.

Your PSU, providing it is a quality unit, could theoretically handle 100% load and review sites like Johnnyguru test then at 100% or as close as they can load it (within a few %).

I see it recommended that you spec a PSU not based on the maximum power but in order to keep your systems typical load around 40-60% of the capacity. That gives plenty of head room for the maximum system load to be under the rated capacity and also keeps your system in the most efficient area of The PSU's load for your typical loads.

For example, my system (980ti +5960x, both overclocked) draws around 350-650 watts gaming depending on the game, so I got a 1000 watt platinum PSU that is over 90% efficient during that normal loading. I tested maximum possible load and was in the neighborhood of 700-750 watts, so I have plenty of head room. I did plan to get a second video card at some point, which is why I chose a 1000 over an 850-900 watt which would have been more appropriate.

 

[swapjim]

My calculations go for 450w. Adding 1.5x to that goes to 675w. So I need a 680-700w PSU?

If yes, then... Wouldn't that be a problem when I draw under 20% of the PSU's power? (I'm reading that PSUs don't play nice when drawing less than 20% of their load).

This is going to be when I don't use the GPU at all and only put a 20-30% load on the CPU. When browsing the web for example.

 

[lehtv]

You're definitely not using 450W with those components.

MOBO: Asus H170 Pro
CPU: Intel i7-6700
RAM: 2x8GB DDR4 2666Mhz (total 16GB)
VGA: AMD Radeon R9 380 4GB
SOUND: Audigy 2
HDD: WD Black 1TB SATA III 7200RPM
SSD: not yet, but pretty soon
OPTICAL DRIVES: Blu-Ray recorder, DVD recorder
FANS (3 in total): custom cooler on the CPU (Arctic Freezer i11), one fan in front of the HDD, one fan at the back of the box pushing the air from the CPU cooler outside
USB DEVICES: two 2.5" external HDDs of 2TB each that power from USB only, my mouse, my keyboard is PS/2 but in the future I might get a USB one

CPU ~80W
Graphics ~200W
The rest maybe 50W, 70-80 W if we're generous

Overall you'll be using 350W at most (peak wattage), usually you'll be using much less because the CPU and GPU will rarely be taxed to 100% load simultaneously. Typical gaming wattage should be under 300W. If you're not going to overclock the graphics card, you could undervolt it instead, which would take another 10-20W off.

A 500W unit is fine for your system, provided it's high quality, of course.

Also, I did the Outervision calculator with your parts and got (using 8h/day utilization):
Load Wattage: 430 W
Recommended PSU Wattage: 480 W

Not only is the load wattage overestimated by almost 100 watts, but the recommended PSU wattage shouldn't be just 50 watts above typical load wattage, more like 50 percent. As a bare minimum, a high quality 480W unit would be fine for a 430W system, but it'd run very noisy and might not last more than a couple of years.

 

[swapjim]

As a bare minimum, a high quality 480W unit would be fine for a 430W system, but it'd run very noisy and might not last more than a couple of years.

I'll read again your post and might add some further comments, but for now I'll say that I want this whole build (and this includes the PSU) to last for a good 3-6 years. So I'll go with a 500w. Should I look at 550w or is it too much?

I'm considering a Corsair or Thermaltake PSU. They seem like nice brands. My current PSU is an Antec 500w. But Antecs are not available anymore in the local market.

 

[lehtv]

500 or 550W - doesn't matter. Even 650W would be fine, it's not like there's any harm to having some extra capacity, other than the higher price you typically have to pay for a bigger unit. 750W I would consider overkill for this build, since 650W can handle any single graphics card and your H170 board isn't designed to run more than one graphics card.

I would not buy Thermaltake. Some are good, others not so much, typically the good ones are a little overpriced. But Corsair RMx, RMi, HX(i) and AX(i) are all excellent. RM550x and RM650x are probably your best bang-for-buck options out of those. Other units you might want to look for: EVGA gold rated units (GS, GQ and most of all G2), Seasonic G-series, XFX XTR series, Super Flower Leadex series. If you don't mind not having modular cables, XFX TS series is good too. And if you want to cheap out and lose some efficiency but still get reliable power, Seasonic S12II and M12II series units are good.

 

[swapjim]

I can find a Crosair VS550 from a store that has excellent RMA (for a very reasonable price) and a Corsair RMx 550w from store that has unknown quality RMA (I'd like to avoid sending PSU overseas*). To get the Rmx 550w from a store with a good RMA I need to pay double the price of the VS550.

Will the VS550 also do?

I can also see a Cooler Master G550M and B500 for very reasonable prices. Actually the B500 is suspiciously cheap.

* Yes, it has happened. A quality PSU simply died on me. It was an Enermax, and it was about a decade ago. I remember it was golden coloured and it's cooler would keep spinning even after the computer was shut down. That was in order to cool down the internals. Smart.

 

[MrTeal]

I can find a Crosair VS550 from a store that has excellent RMA (for a very reasonable price) and a Corsair RMx 550w from store that has unknown quality RMA (I'd like to avoid sending PSU overseas*). To get the Rmx 550w from a store with a good RMA I need to pay double the price of the VS550.

Will the VS550 also do?

I can also see a Cooler Master G550M and B500 for very reasonable prices. Actually the B500 is suspiciously cheap.

* Yes, it has happened. A quality PSU simply died on me. It was an Enermax, and it was about a decade ago. I remember it was golden coloured and it's cooler would keep spinning even after the computer was shut down. That was in order to cool down the internals. Smart.

The VS550 is not a great unit. That being said, the RM550x isn't twice as good. Can you give us a little more insight into the prices you're seeing? I wouldn't pair a cheap PSU like the VS550 with what you have, especially considering the RM550x is $80 in the US. You obviously aren't, but unless the other Corsair is ridiculously overpriced it might be worth it to spend the extra money.

 

[lehtv]

To get the Rmx 550w from a store with a good RMA I need to pay double the price of the VS550.

Well, RM550x is worth twice as much as VS550, in my opinion, especially for a build like yours. You get much better quality internal components, better quality fan, better efficiency, much quieter operation, modular cables, and 7 year warranty (as opposed to 3). VS550 is a low end unit more suitable for budget systems (though still to be avoided if there are better quality choices for not much more money, e.g. S12II or XFX Core).

How much does the RM550x with "unknown quality RMA" cost, then?

I can also see a Cooler Master G550M and B500 for very reasonable prices. Actually the B500 is suspiciously cheap.

G550M is pretty good overall (techpowerup). Its weak point is the use of Chinese low end CapXon capacitors. Capacitor quality is the number one thing you should care about when choosing a unit with longevity in mind - ideally, you'll want a unit with all Japanese capacitors, though review sites like JonnyGuru no longer penalize units for using Taiwanese Teapo capacitors either, so those are probably just fine too. It's mostly the Chinese caps that you should avoid.

Other than that there's not much to complain about. Cooler Master even gives it a 5 year warranty; almost all other units that use CapXon caps only get 3 years. It's good enough that I'd recommend it at the right price - what does it cost compared to RM550x?

Cooler Master B series is crappy, do not buy.

 

[Bearmann]

...I see a concesus for B, so B it is then!

Thanks everyone!

No. A is the correct answer.

 

[swapjim]

No. A is the correct answer.

Damn! I made that mistake myself!

Lets see some prices:

- Corsair VS550 -- 70 EUR (shop with good RMA)
- Corsair RMx 550W -- 110 EUR (shop with unknown RMA, not available anymore on stores with good RMA; must be in shortage)
- Corsair RMx 650W -- 140 EUR (shop that has okay but not great RMA)
- Corsair PSU 600W CX600 -- 90 EUR (shop with good RMA)
- Corsair CS550M (550W) -- 105 EUR (shop with good RMA)
- Cooler Master G550M -- 78 EUR (shop with good RMA)

If Corsair CS550M is just as good with the RMx 550, I'll go with that. Otherwise, I think that my best choice is to go with RMx 650w (yes, it's an overkill but it sounds like the best quality out of my list) or G550M (a well-rounded choice).

 

[MrTeal]

What's the store with the good RMA, and do they carry anything other than Corsair or Coolermaster?

 

[lehtv]

Regarding those RMx units, I wouldn't pay 30€ extra just for "okay RMA" versus "unknown RMA". Chances are you'll never have to RMA it anyway, failure rates are in the single digit percentages. Granted, you'd also be paying for 100W more capacity, but it's not certain you'll ever need the extra capacity.

CS550M isn't as good as RMx, hence I didn't mention CS series in the first place . Let's see:

• It's built by Great Wall which is good but not as good as CWT (workmanship is not quite as high quality)
• Fan uses a cheap sleeve bearing which has lower MTFB than the rifle bearing used in RMx
• Fan spins all the time (though it is quiet); RMx's fan is semi passive which is even quieter
• Cables are semi modular (RMx is fully modular)
• Voltage regulation is pretty good (1-2%) but not top notch like RMx (<1%)
• Warranty is mere 3 years, while RMx has 7 years; tell me which matters more, unknown quality RMA with 7 year length, or known quality RMA with 3 year length? Also, you'll probably be able to RMA directly through Corsair
• Worst of all, it uses lower quality Chinese capacitors, this alone makes CS series not worth buying in my book

All in all, CS550M is much like Cooler Master's G550M series.

The only units I'd buy are the RMx on that list.
VS550 -> trash bin
CX600 -> too expensive for what it is, might be worth it at about 60&#8364;
CS550M -> too expensive compared to RMx which is superior in every way
G550M -> the price is pretty good, but if you can afford an RMx you should buy that instead

What's the store with the good RMA, and do they carry anything other than Corsair or Coolermaster?

This. Maybe if you just link the shops you're using? Language isn't a barrier, we have Google Translate for that.

 

[swapjim]

Well, first thanks for your willingness to check a foreign website! Lets see what we've got.

This store is recommended by everyone for their excellent RMA:

http://www.msystems.gr/index.php?category=1210

That link will take you straight to the PSUs. All following links will do the same for each store.

This store is recommended by a few people in forums as having an adequate RMA:

https://www.priveshop.gr/product/category/19/TROFODOTIKA

The third is new on my list and if I was writing this 24 hours ago I wouldn't have included it. I just bought something today. They told me that for most PC components I have the choice to return it to them and they'll take care of it. The person I talked to seemed reasonable and helpful. The store seemed like it was made out of serious hobbyists that turned to professional. But that's just my first impression.

http://www.pc1.gr/showlist.php?SearchCat=200&SearchSubCat=ΤΡΟΦΟΔΟΤΙΚΑ#

While I was at the store, I glimpsed at a Corsair RMx. I asked if they have the RMx 550 and it appears that they do! The exact name they have it listed on their website is CORSAIR RMX SERIES RM550X 550W 80 PLUS GOLD CERTIFIED FULLY MODULAR (I actually opened this topic in a desktop at the cashier to see if the PSU he has is the same you recommended ) and it indeed has 7 years of guaranty. Wow!

And it only costs 110 EUR. I think I'm going to get that.

 

[lehtv]

Selection is pretty poor at msystems.gr. G550M and G650M are okay, the rest are too bad quality or overpriced.

priveshop.gr has nothing interesting.

Finally at pc1.gr you have a good selection of brands at good prices. Several choices depending on how much you want to pay:

XFX TS 550 Bronze 73&#8364; - Good no frills unit, better than CM G550M but efficiency is lower.
Seasonic M12II-620 80&#8364; - Good unit with fully modular cables and Bronze efficiency. 80&#8364; is a good price for this. Quality is on par with the above but overall a better deal due to modular cables and 70W more capacity. Quiet up to about 300W load, can be noisy beyond that.
Super Flower Leadex 550W 107&#8364; - the unit EVGA 550 G2 is based on. Warranty is 5 years, EVGA offers 7.
Corsair RM550x 111&#8364; - Comparable to EVGA G2 and SF Leadex.
XFX XTR 650W 115&#8364; - Modular, highly efficient, very reliable. Basically an RM650x but with 2 years less warranty and noisier fan. If you don't mind those, 4&#8364; is a very small price to pay for an extra 100 watts.
Corsair RM650x 122&#8364; - Comparable to EVGA G2 and SF Leadex. Probably the priciest unit you should consider - it has all you could want plus extra 100w capacity.

Now that I wrote all that, I would scratch XFX units and SF Leadex off of that list. It boils down to:

want to go "cheap"? -> M12II-620
want Gold efficiency and 7 year warranty? -> RM550x or RM650x

 

[MrTeal]

I would agree with lehtv's suggestion on the RM550x. The M12II-620 is a well built unit, but you likely won't need the extra 70W unless you do a big upgrade, and there's a few minor downsides to it as well. You lose some warranty, a hybrid fan mode, and a bunch of efficiency. I'd pay the extra 30&#8364; just to avoid a group regulated design, but apparently the new updated platform is supposed to be better. I didn't see any good reviews where it was tested though.

That being said, you probably can't go wrong with any of the ones listed. If you've got a white case and think the Leadex one would look awesome, that might be reason enough to switch.

 

[swapjim]

I have one question. The RM550x is the same model with RMx 550w?

 

[MrTeal]

I have one question. The RM550x is the same model with RMx 550w?

Yep.

 

[swapjim]

Excellent! That's the one I'm buying.

Thanks everyone who responded to this thread! And a double thanks to lehtv and MrTeal for diving into the PSU in my local market!
http://forums.anandtech.com/member.php?u=285063

 

[Fizzy Coca-Cola]

As an electrical engineer, I can tell you that you will likely never NEED a PSU that's 120% of your max use, but you WILL see power spikes due to anomalies, and you should be prepared for those. Furthermore, the closer your PSU gets to its max output, the lower the output voltage your CPU etc will see. This means you will be slightly unstable at load. If you plan to overclock, get the highest rating and 80+ cert PSU you can feasibly budget, because you're going to want rock sold voltages. also, get a 8+ cpu pin motherboard if you havent bought one yet, this will solidify CPU voltages. Similar story with GPU power.