What will to much power do?



Hi! I was wondering if anyone could answer this question I have about power supplies: If you have more watts then you need on your psu, will something bad happen to the computer? (for example, the motherboard dies or something like that.) I’m thinking about doing my first computer build, and this question has been haunting me for almost a month now.


It won’t overload the computer.

The worst that will happen is that you will have a very slightly higher electric bill, wasting a bit of energy.

Most people don’t need extremely powerful psu’s. You have to be running a lot of drives, and or very high end video cards to justify them. I have 400-450 watt psu’s in my machines and they are probably more than I need.

It is very important to choose a good manufacturer though, and get a psu that is rated at 80+ efficiency. Look at Corsair, Seasonic, Fortron Source, PC Power and Cooling, as some of the better makes of power supplies.




If you want help building a system (selecting components) we can help. Start a new thread and give a budget and what the PC will be used for.


I’m running a Corsair 620 watt with 4 hdd’s and 4 burners along with a 9800GT video card and 2 PCI SATA
cards and 1 PCIe SATA card along with a Phenom II X3 720 and 4GB of Ram and it never even strains the
PS at all even with all 4 burners in action and working all 4 hdd’s at the same time. Like the old saying goes
(You Can Never Have To Much Power) but a lot of PS’s in the 1000 watt and up is just overkill for most systems
unless you are a hardcore gamer with say dual ATi 4870X2’s in crossfire and a CPU and memory that is so far
overclocked that it is ridiculous. :eek:


Three things:
1)A quality PSU, no matter what wattage rating, is unlikely to damage your computer. A junk PSU (I.E, most of the ones available to buy) might damage the computer regardless what wattage they lie about it being able to handle. (I usually recommend Corsair - their PSUs are made by Seasonic and Channel Well but are still rather nicely priced)
2)Power supplies have varying efficiency over different loads, and usually have lower efficiency at very low loads (seen as a percentage). An average computer probably idles (which it does most of the time) at 70-100W - a 1000W PSU from a manufacturer will typically waste more energy than a 400W one from the same manufacturer. The size of a PSU should be the max consumption under load for all the components plus a bit more for future expansion plus a bit more for PSUs performing worse after aging plus a bit more because efficiency tends to drop when you get too close to its rating. 400W should be plenty for most systems. Many hardware manufacturers unfortunately suggest far more powerful PSUs than what is actually required. I expect this is for two reasons, they want to avoid tech support and/or returns if someone tries to use their product in a machine with a too weak PSU. The other reason being that manufacturers of cheap PSUs tend to lie about how much power it can handle. Also, since the amount of power a computer requires on different voltages has changed over the years, an old (more than about a decade) PSU is unsuitable for a new computer and vice versa.
3)I got distracted when writing this and forgot what the third point was, but it was very clever and informative. :slight_smile:


Both my video card and my CPU need power overhead, so I have a 750 watt one. Cost and cost use not much more than a 450 watt one and I run lots of fans.


[QUOTE=CCRomeo;2451080]Both my video card and my CPU need power overhead, so I have a 750 watt one. Cost and cost use not much more than a 450 watt one and I run lots of fans.[/QUOTE]

Same with me here I have a Phenom II x940, GPU 260GTX that requires alot of power to run them when playing games so I shelled out the dough to cover myself when I do run them. This to me is worth the money and headache. And as the MOD says mine didn’t cost me as much but had 80% eff already. And I did a price check plus check the specs on Newegg so that is how I decided on the PS.


Todays systems and power supply units only get what they need, nothing more. If you have a 500 Watt PSU and your entire system needs 250 Watt in total, it will only draw just that.

If you use old(er) computer components they might always ask full power on anything.

Thanks to energy saving components (if your cpu is doing nothing, it won’t draw much power, harddisk sleep mode, etc) the power consumption these days is greatly recuded.

What kills most systems isn’t really the power consumption, but the unstable currents that cheap PSU’s give off.
12 Volts needs to be 12 Volts precisely (or put it scientific: 12.000). If the currents fluctuate too much and/or are below the specifications you can get all kinds of strange errors on your system.


I found out the hard way about bad PSUs. This old one fried up my eMachine a few weeks ago.