Is there an advantage to having a higher wattage PSU if not needing the wattage?

[Delicieuxz]

Such as, are the parts more durable if they're rated for a higher wattage than you'd actually use - and would your system load be easier on the PSU if the PSU has more headroom? Could the extra headroom result in a PSU lasting longer?

 

For $10 more, I could buy an 850 watt PSU instead of a 750 watt one. My system is planned to be a 5800x with an rtx 3080, and shouldn't need more than 750 watts.

[Stahlmann]

The peak efficiency of a PSU is somewhere between 40-50% of max load afaik. So with your targeted specs you would likely have better efficiency when using the exact same PSU, but at 850W capacity. Also it won't have to work as hard to stay cool and thus will be quieter. Here is an example:

[Parideboy]

Watts tell only part of the story. What matters the most is the quality of the psu.

 

As a reference you can check out this thread:

 

If both are of the same tier, yeah the higher the better.

[Delicieuxz]

I'm specifically comparing the Corsair RMx 750 to the RMx 850, BTW.

[GoldenLag]

2 minutes ago, Stahlmann said:

The peak efficiency of a PSU is somewhere between 60-70% of max load afaik

thats not the case, look at efficiency curves to see where it actually lies. 

 

8 minutes ago, Delicieuxz said:

For $10 more, I could buy an 850 watt PSU instead of a 750 watt one. My system is planned to be a 5800x with an rtx 3080, and shouldn't need more than 750 watts

which units specifically. same unit?

[SupaKomputa]

5800x + 3080 wont use anymore than 550w.

The only excuse for not having a bigger PSU is price.

If only $10 more, i don't think it would hurt.

Maybe there's a reason why that 850w is only $10 away, check the reputation.

[Delicieuxz]

Just now, GoldenLag said:

thats not the case, look at efficiency curves to see where it actually lies. 

 

which units specifically. same unit?

It's the Corsair RMx 750 and the Corsair RMx 850.

 

I added that information at about exactly the same time you posted.

[Stahlmann]

1 minute ago, GoldenLag said:

thats not the case, look at efficiency curves to see where it actually lies. 

My post was already edited.

[ItsMeRachata]

15 minutes ago, Delicieuxz said:

Such as, are the parts more durable if they're rated for a higher wattage than you'd actually use - and would your system load be easier on the PSU if the PSU has more headroom? Could the extra headroom result in a PSU lasting longer?

 

For $10 more, I could buy an 850 watt PSU instead of a 750 watt one. My system is planned to be a 5800x with an rtx 3080, and shouldn't need more than 750 watts.

You should buy a PSU that is double the wattage of your PC wattage as at about 40-60% usage it is the point for peak efficiency. So for your 5800X and 3080 should be about 450W. I would say spend the more 10$ because it is going to make your PC room for upgrade down the line(better GPU)

[Dedayog]

7 minutes ago, ItsMeRachata said:

You should buy a PSU that is double the wattage of your PC wattage as at about 40-60% usage it is the point for peak efficiency.

Let's just post the actual efficiency curves since we're all stabbing at it...  

 

https://www.tomshardware.com/reviews/corsair-rm850x-v2-psu,5568-5.html

 

vs

 

https://www.tomshardware.com/reviews/corsair-rm750x-v2-psu,5585-5.html

 

 

 

 

 

 

[GoldenLag]

8 minutes ago, Stahlmann said:

 

 

Spoiler

 

 just being a bit picky, but that is a very odd graph considering system load is not liniar. 

 

Spoiler

taken from the tomshardware review. which gives a better picture in my humble opinion

 

6 minutes ago, Delicieuxz said:

It's the Corsair RMx 750 and the Corsair RMx 850.

 

I added that information at about exactly the same time you posted.

wouldnt make a big difference afaik. so its entirely up to you if you want to pay the extra. 

 

if you are US located, the Rev DF usually goes for 130 for the 850w model. 

[Stahlmann]

1 minute ago, GoldenLag said:

 just being a bit picky, but that is a very odd graph considering system load is not liniar. 

Source: https://www.guru3d.com/articles-pages/corsair-rm850x-(2018)-power-supply-review,2.html

[GoldenLag]

4 minutes ago, Stahlmann said:

Source: https://www.guru3d.com/articles-pages/corsair-rm850x-(2018)-power-supply-review,2.html

not saying its incorrect, i just preffer the graph to be liniar. as it shows how the effiency is per load more easily. 

[Ankerson]

1 hour ago, Delicieuxz said:

Such as, are the parts more durable if they're rated for a higher wattage than you'd actually use - and would your system load be easier on the PSU if the PSU has more headroom? Could the extra headroom result in a PSU lasting longer?

 

For $10 more, I could buy an 850 watt PSU instead of a 750 watt one. My system is planned to be a 5800x with an rtx 3080, and shouldn't need more than 750 watts.

 

Well normally, ideally you want to be in the in the 40% to 65% load range to be in the sweet spot efficiency range depending on the actual PSU.

 

You really don't want to go over 75% ideally, listen to some and they will have you at 95% or more load. 

 

The more headroom the better within reason, wouldn't get a 2000W PSU for a system that pulls 200W as an extreme example.

 

That said if you are getting a 3080 there is nothing wrong with getting a 850W PSU, even a 1000W to 1200W PSU isn't out of bounds at all depending on the actual card and system setup. Some of the 3080s pull more than 450W so actual gaming loads can be more than 650W depending on the system.

 

That would be 76% load on a 850W PSU, 86% on a 750W PSU. And 100% for a 650W PSU.. And that just for a gaming load, not the max system power draw.

 

So in the end it depends on what card you are getting and what you will be doing with it. 

 

 

 

 

 

 

 

 

[mariushm]

In modern power supplies, the variation in efficiency from around 40% load to 90% load is usually 2-3%, almost always less than 5%, so it's hardly worth talking about it. 

 

Basically, as an exercise let's say your computer consumes 300w.

* For a 550w psu that 300w means 55% load, and let's say it's 92% efficient at that load.

This means 300*100/92 = 326w were consumed to produce 300w, so 26w were lost as heat.

* For a 850w psu, that 300w means 35% load, and let's say it's only 90% efficient at that load. This means 300*100/90 = 333 watts were consumed to produce 300w. 

 

So basically, it's a difference of less than 10w per hour. It would take 100 hours or ~ 5 days of running computer at 300w load to waste 1kWh, which costs around 10-20 us cents on your power bill. 

 

The waste is a bit more pronounced at idle, when your computer consumes less than 10% of a power supply maximum load... let's say 30-50 watts. 

 

A bronze efficiency psu may be only 70% efficient - the 80 plus bronze only requires the psu to be at least 80% efficient at 20% load.

A gold efficiency psu may be 92% (or better) efficient at 20% load, but may only be 80-85% efficient at 10%. 

A platinum (or better) psu IS tested at 10% load and - if my memory is correct - it should be at least 90% efficient (I'm too lazy to look it up)

 

So if you like to leave your pc running 24/7 (as a server or just to extend the life of mechanical drives or for whatever reasons), you would benefit from picking a suitable wattage power supply but only if it's a bronze / silver efficiency psu. With such units, the more you get the power consumption towards the 20-50% load, the higher the efficiency. 

If it's a gold or better psu, it won't matter that much.

 

Otherwise there's benefits to using a higher wattage psu - they'll often have bigger heatsinks so they'll dissipate heat better and they may have a "no-fan" / hybrid mode where they don't spin the fan until the power consumption goes above some threshold or the internal temperature goes above some limit. 

Bigger wattage psus will also have bigger size bulk energy capacitors, which are supposed to be picked in such a way to keep the psu running for at least a mains cycle (~16-20ms) if there's a power failure or a hiccup, at full load.   At lower load, the psu should stay functioning for a significant longer number of milliseconds with no incoming AC voltage. 

This can be beneficial if you're in a region with weak or bad power grid where there's power "events" like dropping for a few ms at a time, or brownouts (voltage going down from 230 to 100-150v and back in a second or two)

 

 

[Ankerson]

1 hour ago, mariushm said:

A platinum (or better) psu IS tested at 10% load and - if my memory is correct - it should be at least 90% efficient (I'm too lazy to look it up)

 

Titanium rated is tested at 10% and has to be 90% or better. Has to be 90% or better at both 10% and 100%.

 

Or to be more accurate:

 

115V - 10% load = 90%, 20% load = 92%, 50% load = 94%, 100% load = 90%

230V - 10% load = 90%, 20% load = 94%, 50% load = 96%, 100% load = 91%

 

The really good ones really do run cooler and can have some very impressive efficiency curves. 

 

That's not even getting into the very tight load regulation and very low ripple (Single digit) of the top end units.

 

For the Gold and Platinum PSUs some can drop down pretty close to 80% at less than 20% load. Bronze can be even worse than that.

 

For systems at idle or just normal use they don't pull a lot of wattage, could be like 50W to 100W...

 

So paying attention to what one is buying, actual PSU can be important.

 

One PC I have has a Platinum PSU in it and pulls about 50W to 60W or so idle and is getting around 82% to 83% efficiency, if that was a Titanium PSU it would be 90% at the same load.