Build help How much power do we really need in a power supply - EVGA knows

[Gremlich]

EVGA has this over on their website - a "Power Meter" that can help you determine just how much power you should be buying, at a minimum, when considering a power supply.

I tried it out to see if my 750W was sufficient to run a GTX970 SSC, an FX-8350, 970 chipset, 16 GB DDR3 1600 RAM, 2 SSDs and 3 HDD of storage.

Of course, it's all to sell you a power supply, but, FWiW, after going through the questionnaire, I got a 20% off coupon to get an EVGA power supply (except b-stock) from their website rated between 600W and 750W. You can even refine your query by Efficiency (gold, bronze) and series as well.

So, my current rig has the power it needs.

[Donut]

The problem though, is no power supply should be going over 70% usage otherwise you're burning through more electricity than you need. So while yes you're fine with a 750W, it isn't very efficient and could be costing you a ton of money in the long run

[GeraldEvans]

Everything I've read says that modern power supplies only consume as much as the system demands, regardless of their overhead.

[Donut]

Hook a voltage meter to the power outlet and find out. It spikes quite frequently when the PSU is loaded, sometimes higher than what the wattage is rated on the PSU

[Gremlich]

1 hour ago, Donut said:

Hook a voltage meter to the power outlet and find out. It spikes quite frequently when the PSU is loaded, sometimes higher than what the wattage is rated on the PSU

dude, like everybody has a Fluke just lying around, Plus, I'm running several peripherals like 2 monitors, an external drive or two, bunch of controllers, my engine oil heater, etc...

And, I posted this for those who aren't always building and rebuilding computers. The more they know....

[Spectiis]

Just  get EVGA Supernova 1000 watts. 

[Drum]

AND.... During the planning stages be sure to upgrade your UPS to support the new power demands.

I actually failed at this twice (d'uh), so lesson learned. Squealing UPS when you put that puppy through the graphics check will remind you.

Thanks for the link @Gremlich. Happy Trails. - DRUM out

[CyberianK]

Interesting to know is that most PSUs best efficiency spikes at ~50% load 

curves look like this

(this is a premium curve for platinum certified expect it to be 80 on left and right for a more standard 80plus PSU but the curve itself is similar)

Also a systems peak output is normally not reached for the majority of time. Therefore a best scenario for efficiency is that you select a power supply that is in the mid range of load during idle and light usage and the peak is in the high range but not reaching 100% for peak usage.

Many peoples who buy 1000W+ power supplies in an uneducated decision end up being at very low loads for the majority of the time at the left of the curve only reaching efficient areas during peak load. These peoples waste money both by paying a premium when buying their PSU plus having lower efficiency even when they thought they bought something better. 

One other thing I would never buy a PSU that does not have at least an 80+ certification because those that don't are usually the crap generic ones which fail on you. Of course higher ones (bronze/gold/platinum) are recommended but straight economically if that makes sense depends largely on how long your PC runs. I for example run my PC almost 24/7 and have high energy cost in Germany that's why I use gold certified for ages now. Here a chart that compares the certifications minimum requirements:

[BravoTwoZero]

9 hours ago, GeraldEvans said:

Everything I've read says that modern power supplies only consume as much as the system demands, regardless of their overhead.

Not entirely, the efficiency of the power supply depends largely on the load, so if your power supply is too large, or too small, the efficiency decreases and you consume more power. Overall, you want to be as close to 50% as possible, which is commonly known as a typical load. Also note that is not that dramatic if you're somewhat off, it only matters a few percentages (and few $/€ per year as a consequence).

When it comes to selecting power supplies you can do two things. Firstly, you know every component that is getting into your system and its energy consumption, which is often also rated for every component. This can get tricky, as you have to know your stuff, although there are a lot of calculators out there that do the work for you if you just select your components. Just summing up the Thermal Design Power (TDP) of your processor and graphics card and add 50 watt for all your other components gets close enough as well, although the Thermal Design Power is more related to the thermal energy production (heat generation) and not everyone use the same definition for this (AMD and Intel differ for example). Disregarding the specific discussion behind this, it is usable at least and gives a reasonable enough indication. Once you have your typical load, you multiple it by two (the 50% efficiency factor for a typical load comes in here), and you know which one to buy. For example, the TDP of most modern processors is around 100 watt, a GTX 970 is 150 watt, motherboard and others can be estimated as 50 watt (which would probably be too high still), and you get 300 watt as typical load, or 600 watt as recommended power supply. These are just some rough numbers to get the idea.

Alternatively, if you are not that knowledgeable in this field, just look at the box of your graphics card and buy the recommended power supply that is listed. The graphics card is in all gaming systems the component that uses the most memory, while a processor with motherboard, memory and hard drives is usually closer to 150 watt in total, which is also accounted for in this advice. For a GTX 970, they recommend i.e. 500 watt to 600 watt (I happen to have 500 watt myself with a GTX 970).

[Switch]

 

 

[Pagan-Tempest]

When shopping for a new power supply, always check JohnnyGURU.com before purchasing as they've extensively reviewed nearly every PSU worth owning. But, yeah, you can't go wrong with an EVGA PSU these days, though I personally went with a SeaSonic because I always go with a SeaSonic!

P.S. I received this message when using the linked power meter from EVGA: "We were not able to locate an equivalent or similar EVGA Power Supply based on the information you provided." Weird.

[Pagan-Tempest]

On ‎1‎/‎28‎/‎2016 at 11:54 PM, Turo said:

I know people are super passionate about power supplies, but I gotta admit, I've never had a problem with any power supply I've ever bought/installed, name brand, top of the line, or bargain level... and that's in about 20 years of gaming.  Probably like most things, there are differences, but unless you're pushing things to the bleeding edge, not likely to make a lot of difference to your average gamer unless you are woefully underpowered? 

 

Maybe I'm just power-supply lucky, I dunno.   

As it goes in science and in life, one data point doth not a trend maketh.  You may well be one of the lucky ones. This guy, however, was not.

[Gremlich]

2 hours ago, Turo said:

I would like to come back to this thread and laugh at myself for tempting the fates...  last night, my power supply died.  lol

 

 

OUCH!! you jinxed yourself, now, didn't you. Like when you say, out loud, "The traffic's not bad today"

[Gremlich]

14 hours ago, Turo said:

Buddy of mine is saving the day, shipping me a 1200W Thermaltake PSU ... weeeee

nothing like some overkill. Unless you really need it, of course, what with multiple GPUs, case lights, mucho fans, lotso HDDs, Espresso machine.....