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djb1011 asked on

power supply

I am changing  a power supply that is 360 watts, if I install a power supply that has greater wattage, is there anything that I need to be aware of, such as too much wattage for a certain type of hardware?
Thanks in advance

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Gary Case

8/22/2022 - Mon

Hi djb1011,

Power supply's only operate at the wattage, or voltage you are currently using. So if you have a 800 watt PSU, but you are only drawing 250 watts, it will only use 250 watts, you should be more concerned about getting a under-powered PSU.  But in your case all seems fine.


Alan Henderson

Alienwalker's correct.
Voltage is what's "pushing" current and that's set by the power supply. Wattage is how much the power supply can provide, not how much your computer can consume.

If your wattage is insufficient, voltage can drop off and that creates problems.


Thanks for the extra info Vallis, it actually helped me understand my own answer.
Your help has saved me hundreds of hours of internet surfing.
☠ MASQ ☠

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there is another catch : if the old one is a 20-pin ATX power supply, you best install another 20-pin PS, of the same or higher wattage
Reason : sometimes the extra 4 pins are fixed on the connector, and the connector cannot be inserted because it interferes with other hardware on the mobo (eg caps)
Alan Henderson

Just an aside for non-technical folk.

One of life's little irritants is how often in the media, by people who should know better, electrical units are incorrectly reported.

You often hear them talking about a near catastrophe where somebody was zapped by "500 volts of electricity" (for instance). That's totally meaningless, voltage is the "pressure" across the conductor. You can have 1000s of Volts built up in your comb when you run it through dry hair and it wouldn't knock an ant off course.

On the other hand, many years ago when I was a navy diver - in the 1960s - electrical system voltages in underwater pressure vessels and in compression chambers had to be dropped to 12V from 24V because we found that divers were being electrocuted when their skins were soaked in sea water. The very low resistance of the salty wet skin allowed huge currents to flow through their bodies at 24V DC. Didn't pay to stand in seawater.

Rant over.

Alan Henderson


Too late to build up any voltage in my comb.

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Gary Case

"... is there anything that I need to be aware of, such as too much wattage for a certain type of hardware? "   ==>  Nothing that hasn't been mentioned above.    The key things you have to be sure of are that (a) it will fit in your case (ATX power supplies have a standard size in 2 dimensions, but the length can vary -- longer supplies won't fit in every case);   (b)  it has the right connectors [e.g. 20 vs 24 pin ATX power -- note that most ... but not all ... 24 pin connectors can be used on 20 pin motherboards;  4 vs 8 pin CPU auxiliary power connectors;  PCIe connectors; SATA connectors; etc.  ==> just be sure you know what you motherboard requires;  then confirm that the PSU you plan to buy has them].      A few of the comments above aren't quite complete, so I'll expand a bit ...

High-quality power supplies are certified 80+ (or better -- there are "Bronze", "Silver", "Gold", and "Platinum"designations that indicate even higher efficiencies) ... this means they operate with at least 80% efficiency.     I recommend that you always buy a PSU that is 80+ certified and has active PFC.    This will have lower operating costs than low efficiency units;  and will virtually ensure a higher-quality PSU.

HOWEVER, this certification is only measured between 20% & 100% loading -- it's actually only measured at 20%, 50%, and 100% loading, but the efficiency curve is parabolic, so any unit that passes at 20% and 100% will be fine in-between.    In fact, the 50% point is generally the highest efficiency.    Consquently, you'll get the best efficiency if you buy a PSU rated at twice the normal operating draw of your PC.    But you also don't want to buy such a high-power unit that your "idle" current is well below 20%, as the efficiency will be much lower in that range.    If your PC was designed with a 360w unit, and you haven't made any significant changes (i.e. added a higher-power video card), then I'd recommend an 80+ unit in the 450-500w range ... but not higher.    If you've made changes, you should estimate the typical wattage your system uses, and buy a unit rated at twice that many watts.      If your current PSU is still working, the best way to do this is to simply measure the wattage with a Kill-a-Watt meter [http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU/ref=sr_1_1?ie=UTF8&qid=1310111008&sr=8-1 ].    Otherwise, there are many online PSU calculators that will help you estimate the power requirements for your system -- for example:  http://extreme.outervision.com/psucalculatorlite.jsp