How much Watts is too much? 500 Watt pc Running 700 watt PSU.

[ScurryNoob]

What would Happen if I use a 700 watt PSU In a 500 Watt PC? Would it damage it?

 

[garyshows]

What would Happen if I use a 700 watt PSU In a 500 Watt PC? Would it damage it?

no more the watts the more upgrade and oc room. less watts or bad quality psu= damage

 

[Karadjgne]

There is a balance to psu sizes. Generally a psu performs it's most efficiently at @50-70% of rated power. So a 500w draw pc on a 700w psu is usually fine. This does not take into consideration psu quality. What you don't want is a mediocre 550w psu running a 500w pc. It just means excessive wear on the psu and more heat than is healthy over extended periods at almost full load. You also don't want to run a 1600w monster psu with a 300w draw pc, the load is so low that at idle or barely above, the monster efficiency goes out the window. Normal usage should see no less than 20% and max usage no more than 70% loads to maintain a healthy psu for its expected lifetime.

As to quality, 500w on a junky 700w psu is asking for trouble, 500w on a good quality 700w psu is cake.

 

[royalcrown]

No because it's not like the power supply "pushes" the watts into the computer. It's not like water pressure in a hose. The computer just uses what it needs and no more so having more won't hurt.

The reason people talk about the right sized power suppl is two fold:

GPU companies like to say recommend power supplies that have a much larger capacity than needed. That means the consumer spends more money than they need to.

The other reason is that power supplies have an efficiency "curve" like Karadjgne said. A power supply curve looks like a drawing of a hill basically, with the highest point being the most efficient operation for the power supply. At this point it is outputting the power with the least waste. Lets say this is 450 watts. What you want to do then is find out how much power your system draws at maximum AND when you are doing what you usually do on it.

You want a power supply that has enough capacity to cover your maximum power draw but also try to keep the efficiency bump and the amount of power you use most of the time as close as you can.

Let's say that when gaming your system draws 325 watts, but you only game once in a while and most of the time you surf the net. You may only draw 200 or so watts then. So you'd get a supply with a least your maximum 325 watts and an extra 10-15 percent. Most power supplies won't last as long or will fail if you use 100 percent capacity a lot (unless you buy the really good mid range to higher end units).

Now if you know you're going to game most of the time upgrade, use more than one video card (SLI or Crossfire) or overclock, you need to add a little more "extra" capacity in watts or buy a better quality unit.

Here is a power curve example.



The flatter the hill is the easier it is to run the power supply in the zone where it's most efficient. Usually more expensive and better quality units will have flatter "curves", while lower end is the opposite. Good power supplies don't waste electricity like they used to 10 years ago. Really OLD or modern low end units can have horrible efficiency numbers of only 50 to 60 percent which means that the power supply needs to draw much more power from the wall because half of it is wasted. The more efficient it is the less it has to draw from the wall to give the computer the power it needs. Less is waster leaving more for the computer to use.

So efficiency matters more when picking budget units. Like computer the newer units are much better and constantly improving so it doesn't really matter as long as you have enough capacity.

Here is a more efficient example according to the curve (it's "flatter" across more of the curve or less "hilly".