I picked up a new Seasonic Platinum that I think will do the job.  It gives me a little breathing room so I don't have to stress about it.

It’s not really enough and not worth gambling ruining many components. I imagine the FTW3 will hit 400 watts. Add your cpu, mb, ram, hdds, lights, fans...it’s not good to be running even near max limit on a PSU.

I genuinely think if one is investing in a top tier 3090, then protect your investment with a quality PSU. It’s really a marginal cost compared to the graphics card and it really is vital for system stability and function.

Keep in mind too that power supplies can get noisy and inconsistency if they are at or near their limit... so having good clean headroom will ensure clean power and less chance of crashing under load.

db8000
so wich psu should i get evga or seasonic and how many watts 750 or 850 

Given that most of these psus are $5-10 more for the 850 I'd go with 850 just to be safe. Will run more efficiently and potentially with a lower fan speed too.

850W+ is a good starting point for 3090 especially if you game or constently putting load on your system. Word of advice, if your system underload takes up 650w don't go and buy a 750w, buy the 850w, this way your psu is never actually working at peak. A psu that is constently working near max Wattage will get it's lifespan lowered. I have a ABS PSU I bought back in 2009, it's still working like a champ today because it never used more than 70% of it's supported watts, when my system is underload...

850 - don't skimp a few dollars to ensure clean headroom

 
seasonic FOCUS PX 850 or EVGA SuperNOVA 850 G3

    wich one 

db8000
how manu wat psu do  i need for the EVGA GeForce® RTX 3090, 24GB, XC3 FTW3 Ultra Gaming
 
i have msi x570 unify whit amd 3950 and corsair rm 650 atx  psu 
 
is this enough or do i need to upgrade to 750 or 850 

I've got a 9900K and 2080 Ti with an 3080 FTW3 on order and am considering further upgrades, just got a SeaSonic Electronics PRIME 1300W 80 Plus Gold from B&H for $245, they still have a couple left if you act fast.  You can see my thread in the PSU forum.
 
I've currently got a 650W G1+ and feel undergunned, bought it when I originally built the machine with a low power 2080.

tasso11000
1300 watts is so useless unless you are running sli.

This isn't Reddit. Plenty of people running OC'd setups with watercooling prefer oversized PSU's.  I might end up with a 525w 3080 Ti and a 300w HEDT cpu in the future and needed to upgrade anyway.  Or I could go 2080 Ti SLI if I wanted to.
 
I wonder how many people with problematic 3080's are undergunned on their PSU's.....hmmmm?  Spending $100 more on a PSU that scoffs at large transient loads to run over $2000 in components seems like a safe bet to me.

850w is perfectly fine for you.  Find the one that fits your budget.

Delirious

tasso11000
1300 watts is so useless unless you are running sli.

well, I am running SLI, but if I am not, which it will be once I have a 3080,  It's not useless.   Many considerations for what you have in your case and there's future proofing there.   I always buy as big as I can afford.  

Doesn’t the psu not Run efficiently if you get to high of a wattage and your not even using half its power.? Correct me if I’m wrong.

Oh ok got it. Quick question, I have the 750 watt evga p2, should I have eco boost flipped on or off. I have had it set to off for the past 5 years. 

tasso11000

Delirious

tasso11000
1300 watts is so useless unless you are running sli.

well, I am running SLI, but if I am not, which it will be once I have a 3080,  It's not useless.   Many considerations for what you have in your case and there's future proofing there.   I always buy as big as I can afford.  

Doesn’t the psu not Run efficiently if you get to high of a wattage and your not even using half its power.? Correct me if I’m wrong.

Factually correct but practically wrong.  Here's the 850w Seasonic Prime Gold (predecessor to current Ultra model) vs. 1200w Seasonic Prime Gold (predecessor to 1300w model I just bought):
 
https://www.kitguru.net/components/power-supplies/zardon/seasonic-prime-850w-gold-psu-review/5/
https://pcper.com/2017/05/seasonic-prime-1200w-gold-power-supply-review/5/
 
As you can see, they are pretty much the same at the same power draw, maybe like 2% difference at most, or wasting say 10w more when running at 500w.    I mean, that could really add up, at typical US electrical rates if you gamed for 1000 hours at 500w, you would end up wasting about $1 more of electricity total over that entire time.  Lol.
 
The one significant exception to this might be a lower power system that spends a good amount of time at near idle, where it might make sense to get a lower power Titanium rated supply where it has to be 90% or above efficiency at 10% load.

Delirious

tasso11000
1300 watts is so useless unless you are running sli.

well, I am running SLI, but if I am not, which it will be once I have a 3080,  It's not useless.   Many considerations for what you have in your case and there's future proofing there.   I always buy as big as I can afford.  

^^^^ this....!!! Many of us maybe coming off of highly OC'd SLi fully water cooled Systems (as mine) with 16 Fans on a 200W Fan Controller....OC'd 9900K (can consume up to 375W depending upon vcore)...many Benchmark etc (extrmely high vcore pushed to there CPU's so imagine a 9900K (or 10900K) drawing 400W +, then a GPU at 400W......then all the other stuff......
 
Also consider that a PSU runs "most efficiently and quiet/cool" when its total draw is around 50%-60% of its total rated Wattage......so "Its not useless" ;) ...am I going to sel my Corsair AX 1600i for a cheaper 850W model....nope! Many of us with extrmely high end PSU are running "peak efficiency, wide open to any future builds and in some cases will never buy another PSU in the next 10 yrs" !!
 
......and why in the world would you not want to purchase a high end reputable PSU when youre investing in a 3090 Card...?? Sure hope your running more than 1440p 120 hz Monitor ;)

I just bought a Seasonic Focus 1000w Modular PSU for my new build with a (hopefully) EVGA FTW3 Ultra 3090, i7 10700k combo