Solved Is it just me, or are power supply calculators just completely unreliable?

andrew129260 · Dec 18, 2024

I recently was helping out in another thread, with someone having power issues.

I noticed upon doing other calculators none of them seem to agree on the power needed for the Power supply.

It's all over the place! I put the same parts on all of these sites and most of them are widely different. Some also factor in fans, some don't.

Newegg:

600 - 699 Watts range

Pc parts picker:

525 W needed

Be Quiet:

850W recommended

Cooler Master:

492 W

I usually just go for 750w or higher depending on the GPU, but I feel like it's hard to know what you actually should get. I always tell people to go 1,000w or more if they plan on keeping the pc a long time and want to upgrade it down the road without worrying about upgrading the power supply. Maybe I am missing something....

Thoughts?

Ghot · Dec 18, 2024

As you noticed they're all gonna be different.

I usually figure 650W for everything, and then add the vid card requirements.

Unless they're buying or have a "serious" power sucking vid card...
This is usually adequate...

https://pcpartpicker.com/product/nf2bt6/seasonic-focus-850-w-80-gold-certified-semi-modular-atx-power-supply-focus-gm-850

Power supplies are most efficient at 70% load.
So if you decide the system needs 750W, add another 200W, approximately.

So whatever wattage you decide is needed, multiply that wattage by .30, and add approximately that amount.

andrew129260 · Dec 19, 2024

yeah hopefully the 750w I chose for my system is enough. I haven't noticed any problems yet. I just wish more of these calculators were correct or at least more close.

But thats a good point about just doing a baseline and then adding the gpu cost.

thanks

bobkn · Dec 19, 2024

One complication is that not all PSUs are created equal. A 600W PSU from BrandX may have roughly the same current available at +12V as a 480W PSU from a more reputable maker. I don't know whether the range in the NewEgg calculator is based on that.

I wouldn't buy a PSU that doesn't list its detailed specs.

650W exclusive of the GPU seems generous. But with 80 Plus gold or better PSUs, an oversized one doesn't carry a significant penalty.

wordsworth · Dec 19, 2024

PSU calculators have given me different results over the years. I've gone with 750-850W the last several years but recently in buying a 4070 Ti Super I wanted a 1000W to replace the 9 year old 850W and all Microcenter had for Thermaltake above 850W was a 1350W so I took it. Just as well since I have another 64GB of RAM coming tomorrow.

I think calculators can give you a rough idea but I've always erred on the up side to what they calculate.

hdmi · Dec 19, 2024

650W would have been more than enough for what you currently have, but your RM750x SHIFT has Zero RPM mode so the fan stays completely off even when your rig is under heavy load. So, it doesn't suck up any dust, which means that you don't very often need to open it up to clean it out. It goes to show you're a quick study.

Ghot · Dec 19, 2024

andrew129260 said:
yeah hopefully the 750w I chose for my system is enough. I haven't noticed any problems yet. I just wish more of these calculators were correct or at least more close.

But thats a good point about just doing a baseline and then adding the gpu cost.

thanks

I'm using an old PC Power & Cooling PSU (750W ~~RMS~~ "continuous"), it peaks at 825W.

andrew129260 · Dec 19, 2024

hdmi said:
650W would have been more than enough for what you currently have, but your RM750x SHIFT has Zero RPM mode so the fan stays completely off even when your rig is under heavy load. So, it doesn't suck up any dust, which means that you don't very often need to open it up to clean it out. It goes to show you're a quick study.

Awesome, thanks. I think you mean unless its under heavy load. It's funny, I actually chose it specifically for that feature (even though my case has a dust filter) and also because the modular interface on the side helps with cable management, and my case supported it quite well. Which makes sense being same brand and all ha.

Ghot said:
I'm using an old PC Power & Cooling PSU (750W RMS), it peaks at 825W.

good to know

Ghot · Dec 19, 2024

andrew129260 said:
good to know

Be aware, they don't make power supplies like this any more.
This sucker is non-modular, and has a 10 year warranty.
I've been running it 24/7 for 15-16 years so far.
All the numbers are STILL right on the money.

Marcus Vinicus · Dec 19, 2024

I completed a comparison of various PSU calculators online and these are the results.
Computer used is System One in my PC Specs (aka the system listed in my signature below).

PSU Calculator	Recommendation (watts)
Corsair	1000
Newegg	700-799
PC Builds	634 (underestimated maximum GPU power usage)
Seasonic	750
MSI	1005
PC Part Picker	880

pparks1 · Dec 19, 2024

I've been doing 750 and 850 Seasonic's in my builds. The focus models usually have a 10 year warranty and the vertex models are usually 12. Never had a problem with one, ever.

Marcus Vinicus · Dec 19, 2024

This is one the best sites online for authoritative in-depth PSU reviews.

PSUs - Hardware Busters

hwbusters.com

andrew129260 · Dec 19, 2024

pparks1 said:
I've been doing 750 and 850 Seasonic's in my builds. The focus models usually have a 10 year warranty and the vertex models are usually 12. Never had a problem with one, ever.

Yeah I go between seasonic and corsair.

LTT labs has a great breakdown of power supplies and how good they are.

Corsair RM1000x SHIFT | LTT Labs

Test results and review of Corsair RM1000x SHIFT

www.lttlabs.com

Seasonic Focus SPX-750 | LTT Labs

Test results and review of Seasonic Focus SPX-750

www.lttlabs.com

andrew129260 · Dec 19, 2024

Marcus Vinicus said:
This is one the best sites online for authoritative in-depth PSU reviews.

PSUs - Hardware Busters

hwbusters.com

nice I didnt do too bad

Corsair RM750x Shift PSU Review: They Shifted the Modular Panel! - Hardware Busters

Hardware Busters - Corsair RM750x Shift PSU Review: They Shifted the Modular Panel! - PSUs

hwbusters.com

Almighty1 · Dec 20, 2024

The calculators might not be correct because each PSU is different. The watts on the label means nothing as is it with all the rails at the same time or is it only when some of the rails are used and at what temperature, etc. That was the reason PC Power & Cooling power supplies cost more because the wattage is what you will get continuous with all rails used at the same time.

PerpetualCycle · Dec 20, 2024

In reality, a 14th gen should only use between 250 and 330 (330 = extreme profile aka 14900KS) watts maxed out. A 4090 graphics card will max out at about 450 watts. Everything else maybe 100 watts or so. So all told around 900 watts with everything maxed out, which it will never be unless you are doing extreme overclocking. A 850W - 1000 watt supply should suffice for such a configuration. Just do a little research on the components and ignore the calculators.

Also, graphics card manufacturers list a recommended PSU wattage. The recommendation is based on a whole system, including CPU and etc. It also is an overestimate just like most calculators are, For instance the Asus 4090 recommends 1000 watts. They overestimate to be safe, not knowing your system or quality of the power supply, The overestimation differs by calaculator.

If the PSU is not a single rail, then as already mentioned by @Almighty1, you have to figure out how much power each rail provides wrt your system.

If you are running high end CPU and/or graphics, I would recommend sticking to quality like SeaSonic or Superflower (or rebranded SS or SF). Most PSU sold are rebranded like Corsair, Asus, MSI, etc. etc.

Just a note, if one plans on a 3000 or 4000 series, particular high end (4070+ e.g.), you should get an ATX 3.0 or 3.1 PSU. PSU with this spec are designed to handle the power spikes these graphics cards can produce (without shutting down). None of those calaculators tell you that.

PerpetualCycle · Dec 20, 2024

Marcus Vinicus said:
This is one the best sites online for authoritative in-depth PSU reviews.

PSUs - Hardware Busters

hwbusters.com

Here are a couple of more reliable and in-depth I have used for a long time

Power Archives - Hardware Secrets

hardwaresecrets.com

KITGURU SHORTLISTS: THE BEST POWER SUPPLY OF 2024 - KitGuru

KitGuru presents the BEST PC Power Supply you can buy in 2019. Updated regularly as our team of experts review the latest products.

www.kitguru.net

Helmut · Dec 20, 2024

"Maybe I am missing something...."

A lot of factors, amongst them:

Peaky nature of power draw, main factors are the CPU and GPU.
PSU efficiency.
Voltage regulation.
Ripple and noise.
Cable ratings.

e.g. PSU efficiency. This follows a curve with power draw, a broad peak in efficiency around half the maximum power delivered by the PSU. By implication less noise from the fan.
So it is advantageous from a wasted heat point of view to have a PSU rated at around twice what is required.
That is likely to be a factor in the Be Quiet recommendation.

bobkn · Dec 20, 2024

Almighty1 said:
The calculators might not be correct because each PSU is different. The watts on the label means nothing as is it with all the rails at the same time or is it only when some of the rails are used and at what temperature, etc. That was the reason PC Power & Cooling power supplies cost more because the wattage is what you will get continuous with all rails used at the same time.

Some of us prefer to get PSUs with a single +12V rail.

Ghot · Dec 20, 2024

bobkn said:
Some of us prefer to get PSUs with a single +12V rail.

The only way to fly. ^^

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