How To Determine Your Power Requirements
A Matter Of Simple Addition
While there are many online calculators meant to help you figure out how much power your build will use, they all estimate its maximum requirement. They then take into account the PSU’s peak efficiency at a load of 50 to 55 percent and make a (generous) projection based on those numbers. The drawback is that this method does not consider consumption when the computer is idle, which we already determined is where efficiency often appears worst.
The following table is meant as a guideline, showing you how much power a certain component is likely to use under a specific load. If you know the exact figures for your components, plug them in instead and do the math.
|Component Type||Description||Idle (W)||Load (W)||Number Installed|
|CPU||Current dual-core CPUCurrent dual-core CPU, overclockedCurrent quad-core CPU (Mid-range)Current quad-core CPU (High-end)Current quad-core CPU, overclocked (High-end)Older dual-core CPU (AMD)Older dual-core CPU (Intel)Older single-core CPU||2025354045355535||65909512514090-125125-14060-90||1|
|Motherboard||Current microATX board without graphicsCurrent microATX board with graphicsNormal mid-range board without graphicsNormal mid-range board with graphicsHigh-end boardHigh-end board, overclocked||153020253540||254035504555||1|
|RAM||Current DDR2 or DDR3 RAM, per 2GB moduleCurrent DDR2 or DDR3 RAM, per 4GB moduleOverclocked RAM per module (estimated)||234||456||1-4|
|HDD||Conventional hard drive||2||8-10||Varies|
|SSD||Current solid-state drives||1||4||Varies|
|ODD||DVD-ROM onlyDVD burnerBlu-ray reader/burner||112||61012||1|
|Fan||Normal CPU fan, mandatorySilent case fanPerformance case fan||123||1-323||1VariesVaries|
|Add-In Card||External sound cardTV cardController card||211||82-52||0-10-1Varies|
|Graphics Cards||Current office-oriented cardCurrent mid-range gaming cardCurrent high-end gaming card||10-1616-3025-35||35-7575-180180-375||11-41-4|
|Other||Cold cathode lighting, modding parts, etc.||See manufacturer info||Varies|
Now that we have an idea of how much power each component draws, calculating the overall consumption at idle and under load is easier. Based on this information, we will define a power window in the next chapter and choose the best PSU for the job.
Therefore APFC is only worthwhile if you were to use it with a battery backup system.
But the ATX specification seems to disagree. According to the spec, full load or "peak loading" allows 10% deviation from the nominal voltage for the 12V rail.
Also, Q about the power factor correction. It's probably the most difficult topic to understand. In this case, you say the load would be anything that used power. Are you talking about hardware like a GPU or the internals of the PSU like capacitors and such? Also, say the computer is putting load on the PSU. How is there idle current then?
Somehow, having a low efficiency under a 65W load is less expensive than low efficiency at 500W load, go figure :D.
If you want a PC to last a good 10-15 years you need to take care of it:
Clean dust, replace fans when they fail, replace thermalpaste, check your temperatures from time to time, not turn it on-off-on too fast, keep your Hard drives with some spare space and defraged if they are HDDs....
There is quite some work for a PC to keep their form, but its not like a human can lay down in bed eating cheese and drinking cola looking like a model either.
PSUs however have this strange aura of magic around them since some people vastly overestimate what power supply they need (I got a 700W TT one for a load of 320, go figure) and others buy things that are simply bad products, no matter how high the W are.
I did once burn a PC due to a bad PSU (and I even OCed the damn PC, went down in smoke.. I gotta say it was quite fun, but expensive), so I stay on the safe side (I just simply add an extra 20% for 12v rail amps as long as the price of a quality supply is not doubling).