We dont have the power, capt'n!

[x88x]

Capacitor aging is a non-issue with high quality PSU's. You can expect to see a "good" unit lose about 10-50w over the period of about 5 years. More if you have a unit with poor internals.

Good to know. I didn't think those numbers sounded right...

Lastly, all PSU "calculators" are junk because they grossly overrate the amount of watts you need.

Check out the one I linked (here it is again). I've found it to be pretty accurate for what you actually need. It also has a pretty comprehensive library of known parts, and gives you lots of options for setting up your calculation, so you can actually simulate your real system, instead of just something in the general ballpark. It still goes a bit higher than absolutely necessary, but not much. For example, my system (as of the last time I was monitoring it) would pull around 250W max, during heavy use. Plugging in the specs for my system as of that time into that calculator gives a 'minimum' of 315W and a recommended of 365W. By comparison, the Newegg calculator says 501W. I actually ran a 750W (upgrading to a 1000W once I get it put back together, in anticipation of new hardware later this year), so more than enough for any of those estimates, but I ran basically the same hardware on a 500W for about a year and it was perfectly fine (left the 500W behind because I had shortened the cables and I moved to a new case, not because I really needed more power).

I agree that most online PSU calculators are junk though. My general rule of thumb is that if it was made by anyone who makes or sells PSUs to ignore it.

[Undead]

For example, my system (as of the last time I was monitoring it) would pull around 250W max, during heavy use. Plugging in the specs for my system as of that time into that calculator gives a 'minimum' of 315W and a recommended of 365W.

That, in my book, makes it junk.

My rig consumes around 250-300WDC under maximum load and that calculator tells me that a 400w PSU is recommended.

[x88x]

That, in my book, makes it junk.

It's still worlds better than most. I would guess their algorithm is somewhere around [sum TDP] + 20-30%, which I think is a pretty good buffer.

My rig consumes around 250-300WDC under maximum load and that calculator tells me that a 400w PSU is recommended.

Ah, but what wattage PSU do you actually use? And what is the minimum you would actually put in your system? After all, it doesn't say that this is how much power your config will use, it says this is what size PSU you should get. Remember that most people using calculators like that won't know as much as we do about computers. If someone asked you what wattage PSU they should get for a system identical to yours, would you tell them 300W? Or would you give them a number that would give them some breathing room and bring the load on the PSU down into a more efficient range?

[Undead]

I use a HX450, but I checked my usage with a Kill-a-watt. Mind you though, they can be a little inaccurate sometimes.

I would recommend a PSU that can run their rig at maximum load, counting in overclocks and such. You'll find not many people ever run close to maximum load unless folding on the CPU/GPU 24/7. For example, I would recommend an 800-850w PSU for a GTX 480/580 rig... but under normal gaming load, this sort of rig would only consume about ~500w. And at idle/browsing, probably in the ~150-200w ballpark. There are just waaaaaaay too many different load conditions to recommend a PSU based on getting "best efficiency".

The 250-300WDC figure I gave was with overclocks included, at maximum load. I wouldn't go as low as recommending a 300w, but that's only because it isn't worth the cost over the slightly higher wattage counterparts.

[xr4man]

i'd rather have the calculators err on the side of telling me i need more power than telling me i need less power and wasting money on an underpowered supply that is just going to burn up and possibly damage my other hardware.

[Undead]

i'd rather have the calculators err on the side of telling me i need more power than telling me i need less power and wasting money on an underpowered supply that is just going to burn up and possibly damage my other hardware.

I'd rather use my own knowledge to determine roughly how much watts I'll need rather than use a calculator that will lead me to waste money.

[mDust]

There are just waaaaaaay too many different load conditions to recommend a PSU based on getting "best efficiency".

There's idle/light task, gaming, and stressing...
Here's a link to the test results of a model similar to mine, but I have an X3 which isn't tuned the same. The X4 peaks from 25% to 50% which is actually better than 50-70% since not many people will utilize that much power. The efficiency curve of this probably isn't the best example, but many non-80+ PSUs have a more extreme curve which falls abysmally low on both ends. The heat those PSUs produce bakes the PSU causing premature failure, wastes electricity, and could cause more noise from the PSU fan or even dump heat into the case.
I got my 1kw PSU about 4 years ago and had (for a short period of time) 2 HD 2900 XTs which each peaked at over 200 watts. They idled at around 100 watts each as efficiency was of no concern then. When gaming, my system pulled around 500 watts and folding pulled around 600. It was right in the sweet spot with almost no heat coming from my unstressed X3...though the 2900s were basically a blast furnace.
GPUs were for a few years the cookie monsters of power consumption, which is why we have all these crazy 1kw+ PSUs these days. Today ATI and nVidia are making much more efficient cards and PSU manufacturers are striving for those 80+ rankings. It's no different than household appliances being energy star rated. They all save money over the life of the product which can add up to more than the extra purchasing cost.
So, to the OP, just make sure it has all the features you want, the efficiency curve peaks at the proper wattage, and you have more power than you need...which allows for OCing, upgrades, etc.

Here is a link to the official 80+ list.

[x88x]

Dowaaahhh??!?!? FSP makes an 80 PLUS Platinum PSU? ...I am overcome by a great wave of skepticism..

[Undead]

Yeah, and Kingwin/Superflower currently have the best 550w PSU's currently available.

Platinum efficiency, under 10mV for the minor rails, and 30mV for the +12v, inside 1% voltage regulation. Pretty solid build quality too.

XION and Rosewill are starting to produce better units too (courtesy of the Superflower GoldenGreen platform).

AFAIK the FSP Arum 80+ Gold units are decent as well... don't quote me on that though because I've only seen voltage regulation tests and internal shots. Not sure about their Platinum units yet, either.

I'm quite happy to see all of these previously looked down upon companies pushing out good Powersupplies.

[diluzio91]

i had a rosewill and its still rock solid to this day. its one of the old 550 watt with 2 fans though, dont know if that makes a difference.