[SOLVED] Are online PSU calculators reliable?

[dg27]

So I'm winding down on specing out an i7-9700k system and need to settle on PSU wattage. I used the calculators listed here

Best Power Supplies 2019

I made sure the info was the same in all cases (although the Seasonic was more detailed than the others).

The numbers covered a very broad range:

Cooler Master: 439 W
bequiet: 441 W
MSI: 457 W
Seasonic: 603 W
newegg: 664 W

I'd been planning on an 850 W PSU because I have a lot of peripherals related to audio production and photography: M.2 boot, SSD storage, 3X HDD storage, audio interface, MIDI controller, several external backup drives, 2 scanners, 2 monitors, etc. None of the calculators asked for much detail other than the Seasonic and even that didn't cover a lot of stuff I've got.

Should I stick with my original plan for an 850 W PSU? (I'm figuring on the Corsair HX850.)

 

[thx1138v2]

At best they will give you a "ballpark" number. You can't have too much power. But do your scanners, backup drives, etc. not have their own power supplies?

 

[dg27]

At best they will give you a "ballpark" number. You can't have too much power.

That's what I always assumed.

But do your scanners, backup drives, etc. not have their own power supplies?

Good point I hadn't thought of. Some do, some don't. One scanner, my interface, and my MIDI controller are all USB 2. A couple of external drives are USB 3.

I think I'll stick to my original plan.

Thanks!

 

[NightHawkRMX]

What gpu do you have?

I like to look at the minimum psu wattage fore your gpu and base my system off of that.

 

[FALC0N]

At best they will give you a "ballpark" number. You can't have too much power.....

Yes. Yes, you can have too much power. Just buy this PSU:

https://www.newegg.com/corsair-ax1600i-cp-9020087-na-1600w/p/N82E16817139226?Item=N82E16817139226

And use it to power a 65 watt Athon X2 4600 running integrated graphics, circa 2007. That's WAAAAAY too much power!

 

[NightHawkRMX]

You cant have to much wattage. It will just be a waste of money.

 

[dg27]

You cant have to much wattage. It will just be a waste of money.

A bit confused by this...

So should I stick with the Corsair HX850?

The only other Corsair the builder has is the Corsair CS650. If I want 750 it has to be an EVGA SuperNOVA G3.

 

[NightHawkRMX]

If your hardware draws 600w (ex) and you only have a 400w psu, bad things will happen.

If your hardware draws 600w and you have a quality 850w psu, you will have no problems.

You can never have too much wattage. Higher wattage units will not hurt your system, they will just cost more.

Without knowing your exact hardware its hard to make a reccomendation.

 

[jonnyguru]

https://www.mathgoodies.com/calculators/random_no_custom

 

[dg27]

If your hardware draws 600w (ex) and you only have a 400w psu, bad things will happen.

If your hardware draws 600w and you have a quality 850w psu, you will have no problems.

You can never have too much wattage. Higher wattage units will not hurt your system, they will just cost more.

Without knowing your exact hardware its hard to make a reccomendation.

Thanks. I think I'll just stick with the 850 W.

 

[cryoburner]

What are the other specs of the system? I highly doubt that you would need anywhere close to an 850 watt PSU for a system being used for "audio production and photography". You likely don't need to spend more than $100 on a quality power supply, let alone close to $200.

Most importantly, what graphics card are you putting in the system (if you are even installing a dedicated card)? The graphics card and CPU will be the main components that draw power under load, and the power draw from everything else should be fairly negligible, probably in the range of 50 to 100 watts in total.

Hard drives will generally only draw around 5 to 10 watts each when in use, and SSDs even less. Sticks of ram will also typically not draw much more than around 5 watts each. Components like monitors, speakers, and most scanners and external drives will have their own power cord to get power from the wall, not from your PSU. Something like a dedicated sound card probably won't be much more than 10 watts. Case fans typically less than 5 watts each. An optical drive might get up around 25 watts when spinning up, otherwise next to nothing when not being used. The motherboard chipset will draw some power too, which can vary depending on the board, but it too should be far less than what is used by the CPU or graphics card.

At stock clocks, a 9700K should typically not draw much more than 100 watts with all cores loaded, though heavy overclocking and certain demanding all-core workloads could potentially push that up closer to 200 watts. If the system were just using integrated graphics, I would expect the power draw with all components under load to never exceed 300 watts, and would typically be in the 100 to 200 watt during typical use, and less than 100 watts at idle, so a quality 500 watt PSU would likely be plenty to run the system with a lot of headroom.

With a dedicated graphics card, you would also need to figure in the card's power draw under load, which is usually pretty close to the card's rated TDP. A lower-end card like a GTX 1050 or RX 560 should draw less than 100 watts under load, while more mid-range to high-end cards will typically fall in the 120 to 220 watt range, and some models of very high-end cards can get up near 300 watts. A lower-end card should still run on a 500 watt PSU just fine with a decent amount of headroom, with a mid-range card you might want to move up to around a 600 watt unit, and something like a 750 watt PSU might be a good idea for the high-end models. Unless you are gaming at high resolutions or working in demanding 3D rendering software though, I don't suppose a high-end graphics card will likely be going into your system, in which case even a 750 watt PSU would likely be unnecessary for your components.

 

[dg27]

Thanks, cryoburner for the amazingly detailed response: I greatly appreciate the tme you spent. Since you went to the trouble, I went to pcpartpicker and spec'd out everything (excluding anything that has its own power supply). I hadn't done this for stuff I already own and will be repurposing from my current machine. This should include everything:

2019_0830_i7-9700

That's saying 548 W.

[This is an update. I realized I'd left a storage HDD off the list.]

(Note that pcpartpicker is shooting up a warning about insufficient SATA ports because it's not accounting for 2 SATA pci-e cards.)

I'm using a pretty nominal GPU (RX580) because I do no gaming; it's a low priority.

Here's the rub: I'm having this machine built, so the selection of PSUs is very limited.

The Corsair CX650 80 Plus Certified would cost nothing additional (included in system price).

The next Corsair is the HX850, which would be $120.

In between there are several EVGA SuperNOVAs, from 650W to 850W, and costing an additional $40-$100. I'd really prefer a Corsair.

In terms of system load, I'm a heavy Pro Tools user, which taxes the CPU (that's the whole reason I'm replacing my i7-960).

All things considered I don't think the Corsair HX850 is out of line: It's roughly 6% of the budget.

Thanks again.