What Wattage Power Supply?

Brandon1994 · 10 Nov 2020 at 13:10

I have seen a lot of different answers to this but what power supply do I need/do I need a bigger one?
Nvidia say 750W but ive seen people saying you need well over that?

My current set up:

CASE - Corsair ICUE 465X
MB - MSI MPG Z390 Gaming Edge
CPU - Intel I9 9900k (Overclocked)
COOLER - Gigabyte Aorus 360mm RGB Cooler
GPU - Asus Rog Strix 3090 (Waiting on, Currently installed is a 2080Ti)
RAM - 4x 3200Mhz 8gb Corsair Vengeance RGB Pro
STORAGE - 2x 1TB Adata XPG SX8200 Pro M.2 PCIE SSD
FANS - 6x Corsair LL120 RGB Pro
PSU - Corsair RM850 850w Plus Gold Fully Modular (Currently Installed)

mickyflinn · 10 Nov 2020 at 13:18

You have an 850w so no worries.

METEORIC · 10 Nov 2020 at 13:36

You can calculate it via:
https://outervision.com/power-supply-calculator

But yes, 850W is enough.

pp111 · 10 Nov 2020 at 17:16

Yes it most certainly is enough, yes. Also you have a good one because it has tons of the 8 way power sockets for the CPU and GPU.

adrichardson81 · 10 Nov 2020 at 20:52

750w would be plenty - I'm running a 3080 and a 3700x. I was paranoid at first but draw at the wall is much lower than I expected.

I think you could do down to a good 650w and you'd still be safe.

lee32uk · 11 Nov 2020 at 13:40

METEORIC said:
You can calculate it via:
https://outervision.com/power-supply-calculator

But yes, 850W is enough.

Those calculator sites are not accurate.

METEORIC · 11 Nov 2020 at 14:24

lee32uk said:
Those calculator sites are not accurate.

It'll get you into the ballpark, if nothing else.

I plugged in my specs and it was just about right, give or take 50W, as I can monitor my usage from the plug. If you're that cautious add 200W to the calculated load wattage and buy that.

lee32uk · 11 Nov 2020 at 17:35

METEORIC said:
It'll get you into the ballpark, if nothing else.

I plugged in my specs and it was just about right, give or take 50W, as I can monitor my usage from the plug. If you're that cautious add 200W to the calculated load wattage and buy that.

Checking out reviews is a better way to gauge power consumption.

METEORIC · 11 Nov 2020 at 17:50

lee32uk said:
Checking out reviews is a better way to gauge power consumption.

Yes that too, but the calculator quick and easy as well, it's not completely wrong. Of course use multiple sources.

Reviewers have varying setups so you will need to account for that as well, like whether they isolate only the component or whether observe whole system draw - plus whether their PSU is of good quality as well (each have varying efficiencies at different loads).

t31os · 11 Nov 2020 at 19:23

The suggested wattage is always with some consideration for people buying baked bean tin PSUs, if you're at the recommended wattage(or even a touch below) with a gold rated PSU you'll more than likely be A OK.

lee32uk · 11 Nov 2020 at 20:54

METEORIC said:
Yes that too, but the calculator quick and easy as well, it's not completely wrong. Of course use multiple sources.

Reviewers have varying setups so you will need to account for that as well, like whether they isolate only the component or whether observe whole system draw - plus whether their PSU is of good quality as well (each have varying efficiencies at different loads).

The review will show you the power consumption for the part being reviewed. So if you are looking at a cpu review it will show it just for that unless otherwise stated. Same goes for gpu.

The psu being used is pretty much irrelevant as efficiency isn't going to make that much difference i.e Gold vs Platinum.

METEORIC · 11 Nov 2020 at 21:42

lee32uk said:
The review will show you the power consumption for the part being reviewed. So if you are looking at a cpu review it will show it just for that unless otherwise stated. Same goes for gpu.

The psu being used is pretty much irrelevant as efficiency isn't going to make that much difference i.e Gold vs Platinum.

I'm not here trying to say you're wrong, you do get a bit more accuracy by looking at individual component reviews. But each reviewer varies.

Yes, if they're measuring straight from the PSU to the component the PSU ain't going to matter as much.
If they're measuring from the plug, then yes it does, depending on the load. PSU's are less efficient at low loads, depending on the quality PSU components, so their readings might slightly be off when using another PSU.

Gold vs Platinum might well be very similar, again that is dependent on each PSU and it's individual composition.

The person here is asking for a calculation for their whole machine, I offered a quick easy way to calculate their power, which may be off by 100W-200W but is still in the ballpark.
You're asking them to look at each component for a more accurate, which is also a valid way but is a bit more time consuming, and finding reviews of each and every component can be hard so it falls back to just reading the manufacturer's recommendations (which is likely what the calculator is using in parts).

lee32uk · 11 Nov 2020 at 23:31

METEORIC said:
I'm not here trying to say you're wrong, you do get a bit more accuracy by looking at individual component reviews. But each reviewer varies.

Yes, if they're measuring straight from the PSU to the component the PSU ain't going to matter as much.
If they're measuring from the plug, then yes it does, depending on the load. PSU's are less efficient at low loads, depending on the quality PSU components, so their readings might slightly be off when using another PSU.

Gold vs Platinum might well be very similar, again that is dependent on each PSU and it's individual composition.

The person here is asking for a calculation for their whole machine, I offered a quick easy way to calculate their power, which may be off by 100W-200W but is still in the ballpark.
You're asking them to look at each component for a more accurate, which is also a valid way but is a bit more time consuming, and finding reviews of each and every component can be hard so it falls back to just reading the manufacturer's recommendations (which is likely what the calculator is using in parts).

The psu efficiency doesn't really matter. A gpu review is going to show the power consumption using a good quality Gold/Platinum/Titanium unit. The difference in efficiency is about 4% with a Gold vs a Titanium at half load. So not really anything worth bothering about. Even at full load it is only around 5%. All you are interested in is the power consumption of the gpu under full load. That then gives you the worst case scenario. Some review sites such as Guru3d will also give you a recommended psu size depending on the gpu.

You don't need to look at reviews for every component. The cpu and gpu are the main ones you need to look at. You don't have any other power hungry components in a desktop pc. So fans, storage etc don't use much at all.

For the majority of people a 650W - 850W is pretty much all you need. Of course if you are going super high end i.e 64 core cpu and an RTX 3090 then you would want 1000W or more if overclocking as well.

The op already has an 850W unit anyway, so he shouldn't have any issues.