Deciding PSU for new build

[TweaknFreak]

Hey folks. I'm planning a build as follows-

• 
  ■ Intel i5-8400
  ■ Gigabyte H370 Gaming 3 Wifi
  ■ probably G.Skill Ripjaws 2666MHz 2x8GB DDR4 RAM
  ■ Deepcool Gammaxx GT RGB
  ■ GTX 1080 Ti FE
  ■ WD 4TB 7200rpm HDD
  ■ Samsung 256GB 850 Evo SATA SSD

Add to this a fan controller and 2 RGB strips of 30 LEDs.

For this config, on full workload, should I get the Corsair RM650x or RM750x ?? Bit confused here, but my guess is that I'll need 750 one.

 

[genca]

You will be fine with rm650x. However, if you want you can get rm750x but there is no need for that. And, at what resolution you will play? Your cpu will bottleneck 1080ti at 1080p.

 

[CountMike]

It's better to err on high side.

 

[CRO5513Y]

The RM650X is more than plenty, might be worth looking at the 750 if it's not too much more and you REALLY want more headroom for future upgrades that will consume more power. If ever in doubt the Coolermaster PSU Calculator is pretty useful but take it with a grain of salt (it can never be 100% accurate, but great for estimations) http://www.coolermaster.com/power-supply-calculator/. Hope this helps!

 

[Rexper]

Even the RM550X will be plenty. And the RMx is a great power supply.

During "Torture Loop" the i5 8400 measured 117.5W.
Average load during Furmark measured 245.7w on the GTX 1080ti FE.
Motherboard, ram, HDD, SSD, a few fans, RGB and controller add to 70W at load, according this Power requirements guide.

So you're looking at 433W of power consumed in an intense workload (CPU + GPU 100%, with other components loaded), idle is below 90w, a typical gaming load may be around 300w.
Remember, a good 550W power supply, like the RM550X, is rated and deliver 550W continously, while maintaining in-spec electrical performance. Your system isn't close to that.

 

[TweaknFreak]

You will be fine with rm650x. However, if you want you can get rm750x but there is no need for that. And, at what resolution you will play? Your cpu will bottleneck 1080ti at 1080p.

I'll be gaming on a 4K 60fps IPS monitor. For me I want decent settings, not high refresh rates or Ultra killer graphics

 

[TweaknFreak]

The RM650X is more than plenty, might be worth looking at the 750 if it's not too much more and you REALLY want more headroom for future upgrades that will consume more power. If ever in doubt the Coolermaster PSU Calculator is pretty useful but take it with a grain of salt (it can never be 100% accurate, but great for estimations) http://www.coolermaster.com/power-supply-calculator/. Hope this helps!

I want this config to last me 3 years at the least. Do you think investing in a higher wattage PSU is worth it, given that electronics are becoming more energy efficient in every generation?

 

[Rexper]

Do you think investing in a higher wattage PSU is worth it

No, there is no point if you aren't going to use it. To need more than 650W PSU you'd have a multi-GPU setup. To need more than 550W you'd have an extreme single-GPU, overclocked system.

Frequent myths include "more efficiency, quieter, less heat" with a higher wattage PSU. These are are false.

 

[TweaknFreak]

Do you think investing in a higher wattage PSU is worth it

No, there is no point if you aren't going to use it. To need more than 650W PSU you'd have a multi-GPU setup. To need more than 550W you'd have an extreme single-GPU, overclocked system.

Frequent myths include "more efficiency, quieter, less heat" with a higher wattage PSU. These are are false.

Just out of curiosity, should a overclocked 8600K @ 4.8GHz instead of the 8400 be comfortable with the 650X?

 

[Kasper Jorgensen]

Frequent myths include "more efficiency, quieter, less heat" with a higher wattage PSU. These are are false.

No they are not necessarily false.

1. They run more efficient because PSU tends to have the highest efficiency when loaded with 40-60% of their max capacity.
2. They run more silent because the fans will spin slower when they are not loaded to maximum and on many of the better ones are using semi passive colling.
3. Heat, obviously a higher wattage PSU are not pushed as much as a lower wattage PSU on same system and thus giving less heat.

If you should care about this when buying a new PSU is a whole other discussion but don't say it's fake, because it is absolutely not.

 

[Rexper]

Just out of curiosity, should a overclocked 8600K @ 4.8GHz instead of the 8400 be comfortable with the 650X?

It will be fine with the 550W RMx, still.

1. They run more efficient because PSU tends to have the highest efficiency when loaded with 40-60% of their max capacity.
2. They run more silent because the fans will spin slower when they are not loaded to maximum and on many of the better ones are using semi passive colling.
3. Heat, obviously a higher wattage PSU are not pushed as much as a lower wattage PSU on same system and thus giving less heat.

1. It's more like 30 to 70% of the PSU, depending on the series. In modern power supplies, such as the RMx, the efficiency between 30% and 70% load is within 1%. It is negligible. The point becomes even more moot when you start to consider efficiencies at idle loads, and the different loads OP's system undergo in it's life. If efficiency is relevant to OP, use an overall more efficient PSU, instead of wasting time with wattages. The Cybenetics efficiency ratings are a great guide, the 85+ ratings are also helpful.

2. More often than not, the fans will span faster. Since the PSUs are pretty much the same efficiency, at the same load they will produce about the same heat. That is common sense. PSUs' fan profile usually just work on temperature, not relative load. A higher wattage PSU usually requires a more aggressive fan profile due to the potentially higher power delivery. This is evident in many high quality PSU lines.
An exception is the RMx series, which use a component to also factor relative load. From my observations, Passive operation occurs below 50% on the RMx, no matter the wattage. Nevertheless, all the RMx are quiet.

3. Look at the real load, not relative load. 200W on the RM550x would produce the same heat as 200W on the RM650X, since their efficiency and platforms are almost identical. Relative load is irrelevant in this example.

When it comes to choosing power supplies, calculate how much power your current system and future intentions need. Filter PSUs with sufficient voltage on the 12V rail (at 40C-50C. PSUs derate at higher ambient temperatures, so a 500W PSU rated at 30C may only deliver 450 at 40C). Wattage should be an ignored factor from there.

Cybenetics Power Supply Database This may also be relevant to OP.

 

[jankerson]

Hey folks. I'm planning a build as follows-

• 
  ■ Intel i5-8400
  ■ Gigabyte H370 Gaming 3 Wifi
  ■ probably G.Skill Ripjaws 2666MHz 2x8GB DDR4 RAM
  ■ Deepcool Gammaxx GT RGB
  ■ GTX 1080 Ti FE
  ■ WD 4TB 7200rpm HDD
  ■ Samsung 256GB 850 Evo SATA SSD

Add to this a fan controller and 2 RGB strips of 30 LEDs.

For this config, on full workload, should I get the Corsair RM650x or RM750x ?? Bit confused here, but my guess is that I'll need 750 one.

Either the RMX 650W or 750W is fine, if you want more headroom for future upgrades etc then go with the 750W if it's not too much more than the 650W version.

I personally like the high end 650W and 750W PSU's due to the cables they have for future upgrades.

 

[Kasper Jorgensen]

1. It's more like 30 to 70% of the PSU, depending on the series. In modern power supplies, such as the RMx, the efficiency between 30% and 70% load is within 1%. It is negligible. The point becomes even more moot when you start to consider efficiencies at idle loads, and the different loads OP's system undergo in it's life. If efficiency is relevant to OP, use an overall more efficient PSU, instead of wasting time with wattages. The Cybenetics efficiency ratings are a great guide, the 85+ ratings are also helpful.

2. More often than not, the fans will span faster. Since the PSUs are pretty much the same efficiency, at the same load they will produce about the same heat. That is common sense. PSUs' fan profile usually just work on temperature, not relative load. A higher wattage PSU usually requires a more aggressive fan profile due to the potentially higher power delivery. This is evident in many high quality PSU lines.
An exception is the RMx series, which use a component to also factor relative load. From my observations, Passive operation occurs below 50% on the RMx, no matter the wattage. Nevertheless, all the RMx are quiet.

3. Look at the real load, not relative load. 200W on the RM550x would produce the same heat as 200W on the RM650X, since their efficiency and platforms are almost identical. Relative load is irrelevant in this example.

Cybenetics Power Supply Database This may also be relevant to OP.

1. They tends to peak in efficiency around 50% load so 40-60& is more correct than 30-70%. However you are correct that it is usually "only" around 1% and it is not something i would personally care much about, but yet they are still more efficient at that load. I know that most peoples computers are actually sitting idle most of the time, just web browsing or watching netflix, but for those who have a different usage than the typically and lives in countries where electricity is not cheap, this might actually matters to them.

2. Correct, not sure if this is also true for the Corsair HX, TX and AX lines. Anyway, I said because OP asked about the RMx PSU.

3. Well, I stand corrected on this one. Didn't consider the real load vs. relative load in this case.

 

[genca]

You will be fine with rm650x. However, if you want you can get rm750x but there is no need for that. And, at what resolution you will play? Your cpu will bottleneck 1080ti at 1080p.

I'll be gaming on a 4K 60fps IPS monitor. For me I want decent settings, not high refresh rates or Ultra killer graphics

Good, your i5 will handle 1080ti.Now, if you want this pc to last you 3 years, i would get better cpu. Something like i5 8600k or i7 8700 from intel, or r5 2600x from amd side(im not telling you to buy one of these, just giving you "advice"). And as Rexper said, you will be fine with 550w psu, but if you can afford 650w or even 750w why not. Maybe you will buy another 1080ti to do sli. So, stick with 650w psu and you have nothing to worry about

 

[TweaknFreak]

You will be fine with rm650x. However, if you want you can get rm750x but there is no need for that. And, at what resolution you will play? Your cpu will bottleneck 1080ti at 1080p.

I'll be gaming on a 4K 60fps IPS monitor. For me I want decent settings, not high refresh rates or Ultra killer graphics

Good, your i5 will handle 1080ti.Now, if you want this pc to last you 3 years, i would get better cpu. Something like i5 8600k or i7 8700 from intel, or r5 2600x from amd side(im not telling you to buy one of these, just giving you "advice"). And as Rexper said, you will be fine with 550w psu, but if you can afford 650w or even 750w why not. Maybe you will buy another 1080ti to do sli. So, stick with 650w psu and you have nothing to worry about

SLI is a no-go for me. If my GPU becomes too old to handle current titles then I'll sell it and get a latest one according to my gaming needs. So it's decided, RM650X it is. The problem with 8600K is getting a decent air cooler without any RAM clearance nuisance and also the fact that the ambient temperature is almost 30-40C in here.