Question Which PSU Calculator should I trust?

[miha2]

Hi everybody,

I know that it's a neverending fight, but still... How do I find out which PSU is best for my rig? I visited the PSU Discussion page, and the link there to find the PSU wattage by GPU. That is wrong. Why? Well, because... what if I have, say, RTX 4090 and some "dead" i5 12600K CPU? It consumes, like, almost 100W less than 12900K, as an example, so... does it still require the same PSU as 12900K? All else (fans/storage/whatever) aside. See my point?
So, for Ryzen 9 9950X and RTX 4080 Super as an example,
OuterVision PSU Calculator, for example, reports I'll be good with 800W GPU
Newegg says the same
BeQuiet says I need at least 850, and that will be barely enough, with PSU working at 94%
Seasonic says I'll be good with 750W.

The list can go on (there are a few other calculators) but that's not the point. How do I really find the right PSU for the computer?

Different PSU calculators calculate differently, with different parameters, so it's impossible to say which PSU is right for my system based on this scenario... Either way, I'm planning to upgrade (but not to these parts, no-no) soon, so I just want to know how much power my upgraded PC will consume. And whether my 850W PSU will be sufficient for it. So if there is any reliable way to find it out, I'd really like to learn more about it.

I'm planning (for now, only planning; I don't know much about anything yet, so that can change at any moment) to get something like this:
AMD Ryzen 9 9950X3D
E-ATX mobo (if I can find a good and cheap-ish one)
2x32GB of RAM (I "may" upgrade to 4x32 at a later point)
RTX 5080
And carry my few SSDs and HDDs (and maybe a couple of other peripherals) to the new rig. I have a 850W PSU, so if that will be plenty, that would be nice, I could save a bit on the PSU... If not... how large should it be? 1000W? 1600W? 2000W? A hydroelectric power plant? A nuclear one? A Dyson sphere? (Last few are for joke, of course, but who knows, maybe for the year of 2040 GPU we'd need a small hydroelectric power plant handy....)

 

[Nine Layer Nige]

My number one rule is "Don't skimp on a PSU" just to save £50, $50.

On the other hand, I bought a Themaltake Toughpower PF3 850w to replace a BeQuiet 650w thinking that my new purchase of an RTX 4080 Super and an i7-12700k would need the extra headroom. However, measuring at the wall outlet using a watt meter, it is only consuming 360w max for the entire pc during AI workloads, which is mostly on the GPU. So, I didn't need to upgrade at all from a 650w.
However, intense gaming might create a different set of higher power draw needs, so it very much depends on the use case (whats yours ??).
A decent PSU should be ok for 5-10 years and GPUs are generally getting more power hungry with each generation and an upgrade every, say, 3 years will require foresight, but hindsight always gets us in the end.
The quality of your existing 850w PSU, but you didn't mention make, model ??

 

[miha2]

My PSU is Corsair HX850 Platinum. It is currently 6 years old. (I upgraded for Battlefield V, so do the math, if you want/need to)

The PSUs (in theory; good ones, at least) should last longer than "5-10" years. (Shouldn't they?)

Since I'm planning to upgrade my computer next time sometime in 5-6 years, I will definitely get a decent PSU then. So is it OK to keep it until then, or is it better to replace it as well? But if it's to be replaced... To which? Will 1000W be enough? Or will it be too much? Don't get me wrong, it's not that I'm trying to save a few bucks (although that's highly preferable, but after all, "safety first") so if I need to get a new PSU, I'd like to get the right one. Like, I can get a 1500W, but if it'll utilize only, like, 800W maximum... why pay more, right? So in other words, if I can save a few bucks, why not save it, right? (For example, is Lian Li Edge 1000W good? It's the cheapest 1000W PSU I could find on Newegg. Plus, it'll be available only on 2/25/2025. Is it OK to keep my PSU until then at the very least? I'm not sure just yet when exactly I'll be upgrading, but we'll see, I guess. I'm waiting for those parts to be announced, and see the release date and prices for them; I don't want to pay $2000 for a GPU that costs $1000 at max. (I read an article one day that... I don't remember the details now, but it was something about RTX 3090 to produce and everything else to cost somewhere around $1000 or so and it was sold for $1500. I read that article a long-long time ago, and it may have been deleted not to cause chaos. Imagine angry gamers striking against Nvidia...))