Power Supply Calculator - Capacitor Ageing?


Mar 27, 2012
Hey, I use eXtreme Power Supply Calculator to estimate my power usage and I wanted to know more about the Capacitor Ageing calculator.

What does the ageing percentage convert from in years on average?

I tried 50% and it adds an extra 100 watts to the power usage.

My computer is around 5 years old and I recently used this to select some new parts "CPU, GPU ect".

Is the ageing rate taking the motherboard into account or the power supply or both?

Website - http://extreme.outervision.com/PSUEngine

Thank you.


I would imagine that it only takes the power supply capacitors age into account, since that is what is delivering the power to your build. Aging capacitors in the power supply diminish the amount of wattage it can successfully supply over time. Hope this helps.


Jan 24, 2007
Yes, it does. Check what it says at the bottom of page
" Electrolytic capacitor aging. When used heavily or over an extended period of time (1+ years) a power supply will slowly lose some of its initial wattage capacity. We recommend you add 10-20% if you plan to keep your PSU for more than 1 year, or 20-30% for 24/7 usage and 1+ years."
No idea. But I think the idea of capacitor aging is overblown.

From the Extreme calculator:
"Electrolytic capacitor aging. When used heavily or over an extended period of time (1+ years) a power supply will slowly lose some of its initial wattage capacity. We recommend you add 10-20% if you plan to keep your PSU for more than 1 year, or 20-30% for 24/7 usage and 1+ years."

Do capacitors age? Certainly. All electronics components age. The real question is:
"How great are the actual effects?"

This question comes up all the time:

The PSU calculators tend to be highly pessimistic. After all, if you over specify a power supply, it really does not hurt anything - except possibly your wallet :). And it does help compensate for all of the junk PSU's out there.

I just plugged the specs for one of my systems into the extreme calculator.

One of my systems has an OC'd Q9550, 4 GB RAM, a GTX260-216, a Gigabyte EP45-UD3P motherboard, 3 hard drives and an optical, and a Soundblaster card all powered by a Corsair 750TX. Hey, I was going to CrossFire, but I changed my mind and went with a single nVidia GPU when I built the system.

Running 3 instances of Prime95 to load the CPU and 3DMark06 to load the GPU, it pulls 375 watts from the wall as measured by my Kill-a-Watt meter. Figuring 80% PSU efficiency, the system pulls 300 watts from the PSU.

The extreme calculator using 10% capacitor aging even though the system runs 24/7 says I need 417 watts. For that matter, it says my OC'd CPU needs 169 watts. I know that is not right because, based on actual measurements, the motherboard power regulator pulls 10 amps (120 watts) when overclocked.

Capacitors age, the rate at which they do cannot be calculated by the psu calculator
Variable's such as quality , amount and duration of load, and heat are unknown by the calculator and will vary on a case to case basis
IMO, if you're going to use the calculator your best bet is to increase cpu utilization and peak load to 100% and leave capacitor aging out of the equation
When I am estimating the size of a neded PSU, I use the CPU and GPU TDP's (a reasonable analog for actual power consumption) and crank them into a SWAG (Scientific Wild Assed Guess). I am usually about 10% high compared to Kill-A-Watt power readings. I just consider that 10% to be Mr. Murphy's share.

Then I double that. I like to run my PSU's at 50% - 60% of capacity. I don't care that much about the money saving increase in efficiency, but I do care about the reduction in PSU heat generated.

So, like delluser1, there are a lot of things I do not need to consider.

jsc's method is very good and close to what I do. I look for a review of the GPU that I intend on using. Normally Guru3d and anadtech. Guru3d dropped using Furmark to determine there "Loaded" wattage which I prefer. I find that this comes very close to what I measure at the Wall. Then I apply the 60 -> 70 for my Minumium value, which brings me very close to jsc's 50 -> 60 % after factoring in the wall is about 20% higher than PSU load.

I have Not had a PSU degrade to the point of requiring it to be swapped out within a five year window. My concern is not so much the deregulation as it is on the increase in ripple and spikes on the Output - For me, Good old O'scope to verify that.

I do basically the same, with the same results

My main system is similar to thiers, 3.8Ghz I7 / X58 ( had a 965, now a 930 )
Using a Killawatt, I have tested a few cards of varying power on it
GTS450, GTS8800512 + SLI , GTX260 + SLI, GTX460TOP + SLI, GTX570
Have also tested the cards with a variety of Intel chips and chipsets

My numbers for the GTX 570 are close

I idle ~25w lower ( didn't disable power saving features ) and see 371 av. on the KaW when gaming
( have seen higher peaks up to 407, not often and not real worried about a millisecond or two of that )

They use a ~90% efficient CM psu ( 88.6-90.5-88.3 according to 80+ )
I know, "they only test at 23c", rarely passes 22c in my room and my system is on an open bench

Factoring in 89% efficiency = about a 330 watt DC load
Just under 62% DC load on my 520 watt 85% psu, the math pretty much coincides
( I3-2100 and GTX 570 only draw 300 AC running Furmark with same 85% psu, a good 450w would do for normal use )

Nvidia reccomends 550 watts for a system with the 570 ( Manufacturer's add the 38a )
The psu calculator; 548 watts with my input ( no cap aging, 100% + 100% )
As long as one knows to look for a quality psu with a high amount of it's wattage available to the 12v rail either of the above is fine, IMO

If running power viruses one has to expect that they'll see a higher load ( I do it often, worst I've seen with my config. running 10 mins. of OCCT's PSU Test is 530w )
How much headroom one wants based on doing that is up to them, but unless running those viruses 24/7 no more is needed, again IMO

Future upgrades need to be considered, not in the form of " I'm going to add a HD and a few fans", that's pointless