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Power Hardware

Is It Worth Investing In a High-Efficiency Power Supply? 328

Posted by samzenpus
from the getting-your-money's-worth dept.
MrSeb writes "If you've gone shopping for a power supply any time over the last few years, you've probably noticed the explosive proliferation of various 80 Plus ratings. As initially conceived, an 80 Plus certification was a way for PSU manufacturers to validate that their power supply units were at least 80% efficient at 25%, 50%, 75%, and 100% of full load. In the pre-80 Plus days, PSU prices normally clustered around a given wattage output. The advent of the various 80 Plus levels has created a second variable that can have a significant impact on unit price. This leads us to three important questions: How much power can you save by moving to a higher-efficiency supply, what's the premium of doing so, and how long does it take to make back your initial investment?"
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Is It Worth Investing In a High-Efficiency Power Supply?

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  • by SplatMan_DK (1035528) on Thursday December 13, 2012 @07:16PM (#42282417) Homepage Journal
    Since the waste energy is converted to heat (which may increase the noise or temperature of the machine) it may well be worth the extra cash anyway.

    Saving a few bucks on electricity is hardly the only reason to buy a more efficient power supply.

    - Jesper
  • Re:IMG Tag? (Score:5, Insightful)

    by evilviper (135110) on Thursday December 13, 2012 @07:22PM (#42282471) Journal

    The real embarrassment is that /. has never supported basic tags like <sup> which would allow proper math mark-up. Instead we get all manner of mangled, unreadable blobs for comments.

  • Re:The Maths (Score:5, Insightful)

    by SJHillman (1966756) on Thursday December 13, 2012 @07:25PM (#42282501)

    Not to mention reduced heat output (and potentially less fan noise due to lower heat), important in many scenarios

  • Re:The Maths (Score:5, Insightful)

    by FrankSchwab (675585) on Thursday December 13, 2012 @07:40PM (#42282661) Journal

    Your HTPC server consumes 350W? What the hell do you have in that thing?

    Mine consumes less than 65W running full blast, serves files and 1080p video. I'd say you'd save a hell of a lot more money by downsizing that HTPC rather than just getting a more efficient power supply.

  • by Darinbob (1142669) on Thursday December 13, 2012 @07:54PM (#42282783)

    If you're only factoring just the electricity bill as a factor. But there are also environmental reasons maybe and it's harder to put an unemotional price on that. This is sort of like the people who claim hybrid electric cars are a waste of money since they're only looking at the wallet and not the bigger picture. It's more than just saving a little electricity as well, there is also the slight increase in customer demand, which slightly increases the market forces towards creating more efficient products in general.

  • by ShogunTux (1236014) on Thursday December 13, 2012 @08:00PM (#42282833)

    Perhaps the "pump" part of heat pump completely eluded you, since they do not defy the first law of thermodynamics as you seem to be implying.

    Heat pumps work by having a sink source off of which they are pumping the heat from or away from. Most of the ones I know happen to be geothermal, which work because the sink which they are pumping from maintains a constant temperature year long underground. So, during the summer, the heat they can extract from that source would be cooler than the air above ground, but during the winter be hotter. They do this by extracting the heat from the source sink, rather than producing it themselves.

    So in that respect, they work much like the fan does within your computer, since the air inside the case is much hotter when running than the air outside of the case. The fan can then displace that heat generated inside rather efficiently by just pushing the hotter air inside the case out, while bringing the cooler air from the room outside in without having to require an equal amount of energy to then power those fans as the equipment running inside of it, thus, like the grandparent, requiring less electric energy to power those fans than what the computer itself uses. If this were not so, then it'd make a lot more sense to completely seal computer cases, as the cooling benefit from the fans wouldn't make up for the amount of dust which they bring into the case during operation.

    So the next time you're tempted to call bullshit on a well known physics principle, make sure you double check that you're not making some stupid mistake. Or else you'll end up looking rather foolish again when someone else points out how you don't know what you're talking about.

  • Re:The Maths (Score:0, Insightful)

    by Anonymous Coward on Thursday December 13, 2012 @08:06PM (#42282881)
    Don't sweat it. He's an idiot who thinks that because his HTPC has a 350W power supply that it uses 350W at all times.
  • by mathimus1863 (1120437) on Thursday December 13, 2012 @10:07PM (#42283663)
    How about reliability? I require a PSU that I know is going to

    (1.) Not die within a year of running at 50-75% load
    (2.) Not take any other components of my computer with it.

    Power supply problems are the most annoying to diagnose, because the symptoms usually show up in other components (like apparent RAM corruption, HDD stuttering, etc). I would pay $50 extra for a power supply that is *not* 80-plus if it has stellar reliability, because it means I only have to build my computer exactly once. On that note, the Corsair HX [newegg.com] series power supplies have not only stellar reliability, but also pretty much silent. I refuse to buy anything else, and you can usually them 20% off if you watch slickdeals.

    Efficiency saves you money, while reliability saves you time *and* money. And time is a limited resource for some of us...
  • Re:The Maths (Score:4, Insightful)

    by tom17 (659054) on Friday December 14, 2012 @09:38AM (#42286531) Homepage

    That's a meaningless comparison tbh. The difference is likely that of 'el-cheapo' vs 'upper-mid-range'. The el-cheapo is probably not as stable when you get closer to its rated output.

    An upper-mid-range 400W would probably have been fine.

    Also, a general question on efficiencies; Do the higher power rated PSUs generally have higher efficiencies at lower power outputs? IOW, given 2 comparable model 'high efficiency' PSU's, one rated at 1000W and the other at 500W, would the 1000W one be more efficient than the 500W one at, say, 250W?
    That could make the 'over the top' ones worthwhile even at lower power levels...

  • Re:The Maths (Score:2, Insightful)

    by datavirtue (1104259) on Friday December 14, 2012 @10:07AM (#42286821)

    It is not overkill. The smaller the load and the greater the rated load capacity the more efficient and predictable the output.

    Essentially, resistance increases as more load is demanded or drawn through the power supply. A higher rated power supply will exhibit less resistance at all mid-rang and higher range loads.

    So, if you are using a 600W power supply and drawing 300W you are much more efficient (less heat, less resistance--same thing) than running a 400W power supply while drawing 300W. Higher rated power supplies are usually a better choice over all, but 1000W is "overkill" for a regular desktop machine. A rating of 600-700W with quality components is sufficient for most gaming rigs with dual GPUs, high-wattage CPUs and multiple hard drives. If you spend $15 on a PS don't expect it to run long, and when it does go it could be in a big way.

  • Re:The Maths (Score:4, Insightful)

    by Just Some Guy (3352) <kirk+slashdot@strauser.com> on Friday December 14, 2012 @12:17PM (#42288365) Homepage Journal

    "Not a major factor"? That 120W spread over a year yields:

    120W * (1kW / 1000W) * (24 hours / 1 day) * (365 days / 1 year) = 1050 kWh / year

    I just checked my electric bill; I'm paying about $0.14 per kWh. That gives:

    (1050 kWh / year) * ($0.14 / kWh) = $147 / year

    A 90% efficient PSU is half as wasteful as an 80% PSU, and half of $147 is about $73. If you can pay $73 to upgrade from an 80% efficient PSU to a 90% efficient PSU, you'll get 100% return on investment in one year. That's ignoring the extra cooling demands of the higher efficiency unit (and ignoring the decreased heating demands because electric heat is freaking expensive so $73 in electric heating would offset, what, $10 of gas heat?).

    TL;DR: you're almost always better off buying the high efficiency PSU.

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