Built a new rig and thought I needed to beef up the PSU somewhat (mainly because it was 450watt and I needed pci-e graphic card plugs and didn't want to use too many adapters), used a few online calculators and came to the figure of at least 650w (one site came up with an estimation of 900w! That was Asus though so I guess they were being cautious) - anyway, I bought a high quality 700w unit and carried on my merry way. I had a plugin inline watt meter so I stuck that on last night just to see what the system really is using, at idle it drew around 225 watts, running Adrianne demo and 3Dmark benchmark the most it ever pulled was 340 watt. Did I just waste my time upgrading PSU? I know you don't want to run at the limit, but 450w for a 340watt draw sounds ample enough, 700 sounds like overkill - are the figures PSU manufacturers publish just optimistic BS so you need to go much higher in the real world?
700w is probably over kill but hey the damage is done, the fact that its running much lower load than necessary should make it live longer and potentially improve its efficiency. A 450 would be probably too low but a little more would have done.
This is a system with Q6700 quad core overclocked to 2.96ghz, 5 hard disks (4 SATA in a RAID 0 array), 2x 8800GT with fans in SLI, 3 case fans, 1x Silent Knight II CPU cooler, 2x 2gb DDR2, DVD drive, PCI-E WiFi card, USB DVD drive & USB HDD and it doesn't even break 350 watts when benchmarking.
Most PSU's are overkill -- using a "Kill-A-Watt" inline meter is a great way to figure out your real power requirements. Ideally your PSU should have 20% more wattage than your system has at full load / peak, taking into consideration that most PSU's are rated most efficient at 80%. If your PSU is still fairly new, just replace it with a nice ~500 watt single 12V rail PSU (if you can still exchange them). Of course you can always get something a little bit beefier if you are planning in the long-term (eg. more HD's, new GPU(s) down the road?). I don't buy into the whole 1kW PSU deal... unless I'd be running dual CPU's, 2-4 gpu's, 10-14 HD's, water cooling, etc.
the point of buying double the power requirement of your computer PSU's is for both future upgrades and for it to be operating at optimum capacity. you don't want to have a 350w PSU operating at 350w all the time. you'll want at least a 600w for a 350w machine.
Actually, you want ~75% for maximum efficiency tbh, as per Bindi's latest PSU review there's a good efficiency graph on there. As for upgradeability, most people will get a new PSU at a major upgrade junction, and until then there isn't usually a massive power jump in a system.
50-75 percent is the sweet spot - any more and it'll either be too noisy or you'll stress it in the long term. In future we'll be testing at 20 percent too because that's "idle" and maybe "off" to see what it draws at standby. If you load under 50 percent basically you've overspent imo.
With my watt meter my ~600w psu draws something like 10w from the wall when its off, must try stand by one day I never use it but i'm curious as to what it gets. Can't imagine the psu is very efficient at that kind of level though.
Got mine from Aldi for a fiver. 650W PSU in my PC, pulls around 190W at idle, 270W all guns blazing (E6750, ATI 4850, Asus P35 board and 3 HDDs).
that cheep im off to aldi in the morning lol iv got a 500w psu runing a e4500 runing at 3ghz 2gig ram a bfg 8600 gts on a gigabyte ep35c-ds3r mobo love to no wot power it is using
Was a few weeks ago, as ever with Aldi might have been a local special. Went to top the freezer up with Pizza's and spotted it as I wandered past.
Bah, I'll probably just grab that mappers one then - I've got to go fairly near to a Maplin in the next couple of days anyway (damn split-campus... )
Hmm... thats not a lot of juice for that nutsie system. Impressive actually. Makes me think my 600watt is overkill for my rig. So when a PSU is rated at 80% efficiency, like a 600 watt, its really only rated to draw 480 watts constant, right?
Ever since I got my Kill-A-Watt, I've been collecting this data for every computer I work on. Granted, most of my work is done on office'n'internet computers, but it's still interesting. In my experience, a single-core Sempron or Athlon64 (brisbane, usually; I try to avoid 85-watt TDP processors) with 1gb of RAM and a basic video card will never, under any circumstances, break through 100 watts from the wall. Getting into the types of computers people on Bit-Tech are likely to enjoy, an E6550, 9600gt, 2gb, 2x HDD system will draw roughly 160 watts from the wall (barely 125 watts DC, for a good 80+ PSU). A properly fast system goes up pretty quickly from there, but the effective cap is around 350 watts. Only a very ridiculous system will break 400 watts, and it's likely to require an overclocked quad core and SLI. There are many PSU calculators, and they're all wrong except this one: http://web.aanet.com.au/SnooP/psucalc.php. It's a bit shy of options, so just pick the closest item you can; with approximately the correct parts, this calculator usually estimates within 20% of what my meter reads (and it always estimates high - I've never had a system draw more than calculated, but they frequently draw a few dozen watts less). No, it means the PSU converts 80% of the incoming AC electricity to DC; the rest is turned to heat. The rating is still on the DC side, though, so the result is a 600 watt power supply running at full load would actually draw 750 watts of AC power. A good power supply should be able to provide 100% of its capacity, though doing it for a long time will probably reduce the lifespan of the PSU and generate a lot of extra noise.
http://extreme.outervision.com/psucalculator.jsp Best power supply calculator I've used, very accurate. Though they are missing some up to date parts on there, maybe in the pro version?
