Originally Posted by tipoo
I'm not one either, but whenever I've built PCs and checked power supply calculators for what I should get, there was always over provisioning for capacitor aging. If it didn't affect output, why would that be there? One example:
Well, I just talked to an actual EE, and that calculator is extreme, to put it mildly.
Aging of electrolyte capacitors is mostly a function of how much load you submit them to, by the simple causality: load -> heat -> evaporation of electrolyte. A quality power supply rated at N watts will use reservoir capacitors (responsible for the smoothing of the voltage into 'proper' DC) of both high-quality electrolyte and
of sufficient capacity so that they would not degrade to unacceptable levels below N over the projected lifespan of the device (which can be several decades).
The advice on that site you quoted (that you should go for a larger power reserve over a longer projected lifespan) does help for no other reason than the fact that a higher-power PSU, regardless of its quality, would still use larger capacitors, so when used at lower loads those capacitors will function longer within the expected margins for the PSU. So basically if you have doubts about the quality of the PSU, going with a larger one will buy you some extra lifespan.
But at the same time the site sets the issue of aging PSU's onto the wrong premise. A badly-aged PSU does not produce less DC power per se - in 3 years it will not produce perfectly good DC at 30% less (arbitrary numbers) - no, it will produce power of lesser DC quality. Whether for the device using that power that translates to dropping of some power lines and shutdowns, or the death of some components - that's entirely up to how that device was designed to withstand bad DC. And that is what causes devices to fail when used with aged (low-quality) PSUs. Bottomline being, an aged (low quality) PSU is not 'just as good as new but for lower loads' - it's just bad!