Wattage calculators say I'm at 450watts so would a 550 PSU be plenty then ?

Corsair RMX Series (2018), RM550x is what I'm thinking of getting.


I5-9500

RTX 2060

16GB ram

SSD

2 for HDD storage

3 120mm case fans

No overclocking

Also these online calculators seem to overestimate ?

I would go with a 650 watt. I'm a stickler for trying to operate in the most efficient part of the curve.

550 is fine for that build.

I bet you'd never see that build go over 300 watts in real world use no matter what you did so long as you aren't overclocking.

2060 = 160 watt max
i5-9500 = 95 watt max
Motherboard and RAM 35 ish watts
SSD - basically nothing
10 watts for the two hard-drives.
10 watts total for the three fans.

In real world use these things won't all be pulling max at once...

If you don't OC, it will be well under 450W. If you OC, it can go a little higher. If you OC for some gaming, 650W would be rather on the safe side. If you don't 550 is sufficient, with the high level of quality of that PSU. If you always OC, it would be safer to go for 750W.

550 is likely plenty (the effeciency curve makes sense but isn't my space).

To give you a real-world example.. I'm not saying you should do this . I ran a kill-a-watt before being OK with adding the second 6pin on my CX430. I pulled 400w at peak while running Prim95 and Furmark at the same time.
4770K @ 4.2 (24/7)
980GTX minimal OC
16GB DDR3
SSD
600GB Raptor 10k
2x 140mm
MCP 355 pump

Efficiency drops the closer the PSU is to max output. I think the 80+ rating is a good idea even though the RM550X is 80+ Gold, I would stay within 70% to 80% of PSU max theoretical output. The further you are from max theoretical output the better the PSU performs and the more stable your system can be. Being able to have room for overclock is always a win [H]

deaedius said:

Efficiency drops the closer the PSU is to max output. I think the 80+ rating is a good idea even though the RM550X is 80+ Gold, I would stay within 70% to 80% of PSU max theoretical output. The further you are from max theoretical output the better the PSU performs and the more stable your system can be. Being able to have room for overclock is always a win [H]

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The efficiency drop from 50% to 100% on most quality PSUs is less than 3%. Only in a budget PSU would the efficiency drop be greater than 5%, and you should be avoiding those PSUs for other reasons anyways. The efficiency curve should be the last thing anyone thinks about when sizing a PSU for their build.

If you're concerned about efficiency, it's actually the other direction that has the biggest problem. When you're idling at the desktop you should be well below 10% or 55W on a 550W PSU. Gold PSUs tend to do way better at managing light loads than non gold ones. If you plan on leaving your pc on 24/7 the light load consumption is more important fully loaded. There are PSUs that could be 85% efficient at high loads, but at say a 5% load (25W idle) they are only like 70% efficient. Thankfully this issue was uncovered years ago, and a lot of these Platinum PSUs are actually really good at low power draw.

A 550W would likely work, but it's about the smallest PSU I would go for. The calculators do tend to be conservative, so it should run it without issue. The only thing that could be a variable is Intel's TDP numbers are meaningless these days. So they could be underestimating the power draw of the CPU a bit when it's trying to turbo. You should still have more than enough headroom to account for that.