PSU Wattage Wattage ?

[wowotek]

Hi Guys, I'm sorry the title is little bit confusing. but i'm just wondering, if I have 550w of PSU, is that mean it consume 550w from my outlet ? and what does PSU Wattage mean ? is that can deliver 550watt or Consume 550w? Thank you

[HKZeroFive]

The power supply can deliver 550W. However, a PC only consumes as much power as it needs.

[wowotek]

1 minute ago, HKZeroFive said:

The power supply can deliver 550W. However, a PC only consumes as much power as it needs.

and how much does it consume from my outlet ?

[Trav_X]

Just now, wowotek said:

and how much does it consume from my outlet ?

As many watts as your computer currently needs. For example, if your CPU is using 60 watts, then your power supply will draw 60 watts from the wall. But, if your PSU only has 80+ efficiency, then it could draw up to like 70 watts. But, if it's 80+ Gold, then it may only draw up to like 62-63.

[HKZeroFive]

2 minutes ago, wowotek said:

and how much does it consume from my outlet ?

What's the efficiency rating?

[Enderman]

4 minutes ago, wowotek said:

and how much does it consume from my outlet ?

550 / efficiency = max power draw from outlet

But it will almost always be less because your PC won't draw 550W.

[wowotek]

1 minute ago, Trav_X said:

As many watts as your computer currently needs. For example, if your CPU is using 60 watts, then your power supply will draw 60 watts from the wall. But, if your PSU only has 80+ efficiency, then it could draw up to like 70 watts. But, if it's 80+ Gold, then it may only draw up to like 62-63.

Wow that explain much about efficiency. is that mean PSU efficiency is not affecting the power that it can deliver ? I mean like the smoothness and continuity ? I mean like, if I have 80+ Gold, is that can deliver power more smoothly or only the PSU power consuming efficiency?

[wowotek]

2 minutes ago, HKZeroFive said:

What's the efficiency rating?

well I'm only wondering.

[AdamBGames]

8 minutes ago, wowotek said:

Hi Guys, I'm sorry the title is little bit confusing. but i'm just wondering, if I have 550w of PSU, is that mean it consume 550w from my outlet ? and what does PSU Wattage mean ? is that can deliver 550watt or Consume 550w? Thank you

That is the maximum it can consume, but it will only consume as much wattage as the pc needs

[Trav_X]

Just now, wowotek said:

Wow that explain much about efficiency. is that mean PSU efficiency is not affecting the power that it can deliver ? I mean like the smoothness and continuity ? I mean like, if I have 80+ Gold, is that can deliver power more smoothly or only the PSU power consuming efficiency?

The higher the efficiency, the closer to its advertised wattage it can theoretically get. A 600w 80+ gold can deliver almost up to exactly 600w, probably like 590 but it would be at 100% load. A 600w 80+ Bronze would deliver probably up the same 590 or more, but it would be less efficient, so you would be drawing more than an 80+ gold when your system is drawing the same amount. 

 

Say you have the exact same load on your computer at the same time. Say your components are trying to draw 200 watts. If you have 80+ gold you'll draw very close to 200 watts, within like 5-6% above 200. If you have an 80+ bronze you'll draw a little more than 200, probably closer to 220-230. In that case, you'd be spending more money on electricity because you're consistently drawing more power. 

 

That at does not mean Bronze PSU's are bad. There are Bronze units that use better quality components than gold rated, but their efficiency is just lower by design. Bronze PSU's like the CXM series from Corsair and the Seasonic M12II series are great PSU's that, in terms of ripple, stability, and power delivery are very good.

[wowotek]

2 minutes ago, Trav_X said:

The higher the efficiency, the closer to its advertised wattage it can theoretically get. A 600w 80+ gold can deliver almost up to exactly 600w, probably like 590 but it would be at 100% load. A 600w 80+ Bronze would deliver probably up the same 590 or more, but it would be less efficient, so you would be drawing more than an 80+ gold when your system is drawing the same amount. 

 

Say you have the exact same load on your computer at the same time. Say your components are trying to draw 200 watts. If you have 80+ gold you'll draw very close to 200 watts, within like 5-6% above 200. If you have an 80+ bronze you'll draw a little more than 200, probably closer to 220-230. In that case, you'd be spending more money on electricity because you're consistently drawing more power. 

 

That at does not mean Bronze PSU's are bad. There are Bronze units that use better quality components than gold rated, but their efficiency is just lower by design. Bronze PSU's like the CXM series from Corsair and the Seasonic M12II series are great PSU's that, in terms of ripple, stability, and power delivery are very good.

Thank you, that enlight me a lot

[HKZeroFive]

9 minutes ago, wowotek said:

well I'm only wondering.

As @Enderman pointed out, 550/efficiency (let's say it's a 90% efficient unit, you'd put 0.90 here) gives you the amount of power drawn from the wall under max load.

[mariushm]

If a power supply is rated for 550w, it means it can give up to 550 watts to all devices connected to it.

These 550w are produced with a certain efficiency... if a power supply is said that it has 80% efficiency, it simply means that those 550 watts are just 80% of the whole energy drawn from the mains: 

 

 ? watts --- 100 %

550 watts - 80 %

 

so ? watts  = 550 w * 100 / 80 = ~690 watts.

 

That difference of 20% is power losses due to conversion from 110v AC or 220v AC to the DC voltages the computer needs. The majority of these losses are heat on heatsinks inside the power supply, which has to be pushed outside the computer using the fan installed on the power supply.

 

The power supply won't produce these 550 watts all the time, and just throw them away as heat, it will produce only as much as computer components demand.

 

The efficiency of a power supply is not constant throughout all the output range of a power supply, it's usually a curve, with the peak efficiency usually at about 50-60% of the power supply's output.

For example, here's a review for a 600w rated power supply : https://www.techpowerup.com/reviews/Cougar/LX600/6.html

 

 

So as you can see, this power supply is best for computers that will consume most of the time around 300-400 watts, for example for a system used mostly for gaming with a powerful video card.

Because of these efficiency curves, it's not always the best idea to just go with the most powerful power supply, it's smart to pick the most suitable power supply for the system being built.

For example, it won't be great power supply to use for an office computer with a cheap single or dual core processor and integrated graphics, because those computers will average around 50-60 watts of power and at that point, the efficiency will be around 75% (compared to a peak of 88% at 300w)  so about 20 watts of power are just wasted as heat inside the power supply. For such a system, it would make sense to buy a 350-400w power supply.

 

Also an important note. Power supplies are designed to output three important voltages : 3.3v , 5v and 12v.  Modern computers use 12v to power most components, such as processors and video cards and classic hard drives and fans, while 3.3v and 5v are barely used for SSD drives and some secondary things (little amount of energy).

 

Some older designs of power supplies reserved a particular amount of the power supply's capabilities for 3.3v and 5v, which means that amount of power could only be used to produce 3.3v and 5v. For example, you would have 500 w power supply, but that power supply can only provide 380w on 12v and the rest is reserved for 3.3v and 5v.

 

Newer power supply designs are made to be able to produce all those 500 watts of power on 12v and have voltage converts built inside to convert 12v to 3.3v and 5v, just as much as needed, without reserving so much power that wouldn't be used by parts.

 

You can usually determine what kind of power supply design you have by looking on the power supply that shows a table with the current output for each voltage. If you see that the power supply can output almost all the power on 12v, it's one of the better, newer designs.

 

For example, in the case of the power supply I mentioned above, here's the sticker on the side of the power supply, you can see it's modern design that can output almost all 600w on 12v  (12v x 49A = 588 watts) , and uses dc-dc converters to produce 3.3v and 5v from 12v as needed :

 

[STRMfrmXMN]

3 hours ago, Trav_X said:

The higher the efficiency, the closer to its advertised wattage it can theoretically get. A 600w 80+ gold can deliver almost up to exactly 600w, probably like 590 but it would be at 100% load. A 600w 80+ Bronze would deliver probably up the same 590 or more, but it would be less efficient, so you would be drawing more than an 80+ gold when your system is drawing the same amount. 

 

Say you have the exact same load on your computer at the same time. Say your components are trying to draw 200 watts. If you have 80+ gold you'll draw very close to 200 watts, within like 5-6% above 200. If you have an 80+ bronze you'll draw a little more than 200, probably closer to 220-230. In that case, you'd be spending more money on electricity because you're consistently drawing more power. 

 

That at does not mean Bronze PSU's are bad. There are Bronze units that use better quality components than gold rated, but their efficiency is just lower by design. Bronze PSU's like the CXM series from Corsair and the Seasonic M12II series are great PSU's that, in terms of ripple, stability, and power delivery are very good.

That's most certainly not how 80 PLUS efficiency works.

 

3 hours ago, wowotek said:

Hi Guys, I'm sorry the title is little bit confusing. but i'm just wondering, if I have 550w of PSU, is that mean it consume 550w from my outlet ? and what does PSU Wattage mean ? is that can deliver 550watt or Consume 550w? Thank you

We have a guide pinned on the PSU subforum about this very topic. It's also in my signature. Please read that for any questions. There's an abundance of misinformation in this thread and I can't be bothered to address it all individually.

[wowotek]

2 minutes ago, STRMfrmXMN said:

That's most certainly not how 80 PLUS efficiency works.

 

We have a guide pinned on the PSU subforum about this very topic. It's also in my signature. Please read that for any questions. There's an abundance of misinformation in this thread and I can't be bothered to address it all individually.

thank you for your information, i'll look into that later.

[HKZeroFive]

3 hours ago, Trav_X said:

The higher the efficiency, the closer to its advertised wattage it can theoretically get. A 600w 80+ gold can deliver almost up to exactly 600w, probably like 590 but it would be at 100% load. A 600w 80+ Bronze would deliver probably up the same 590 or more, but it would be less efficient, so you would be drawing more than an 80+ gold when your system is drawing the same amount. 

 

Say you have the exact same load on your computer at the same time. Say your components are trying to draw 200 watts. If you have 80+ gold you'll draw very close to 200 watts, within like 5-6% above 200. If you have an 80+ bronze you'll draw a little more than 200, probably closer to 220-230. In that case, you'd be spending more money on electricity because you're consistently drawing more power. 

The less efficient a power supply is, the more power you'll be drawing from the wall. The more efficient a power supply is, the less power you'll be drawing from the wall. The power supply will not lose output because it has a lower efficiency rating.

 

If your components draw 200W, they will draw 200W. Just because the power supply has a better efficiency rating, it doesn't mean that the power consumption of the components will magically change.

 

A less efficient PSU will not mean that your PC's components will consume more power but rather you're consuming more power from the wall. That affects your electricity bill.

[Trav_X]

16 minutes ago, HKZeroFive said:

The less efficient a power supply is, the more power you'll be drawing from the wall. The more efficient a power supply is, the less power you'll be drawing from the wall. The power supply will not lose output because it has a lower efficiency rating.

 

If your components draw 200W, they will draw 200W. Just because the power supply has a better efficiency rating, it doesn't mean that the power consumption of the components will magically change.

 

A less efficient PSU will not mean that your PC's components will consume more power but rather you're consuming more power from the wall. That affects your electricity bill.

I never said PSU affects your system's power draw. Just when you have a less efficient power supply, you'll be drawing more power from the wall to power the same amount of system.

[HKZeroFive]

7 hours ago, Trav_X said:

I never said PSU affects your system's power draw. Just when you have a less efficient power supply, you'll be drawing more power from the wall to power the same amount of system.

11 hours ago, Trav_X said:

The higher the efficiency, the closer to its advertised wattage it can theoretically get. A 600w 80+ gold can deliver almost up to exactly 600w, probably like 590 but it would be at 100% load. A 600w 80+ Bronze would deliver probably up the same 590 or more, but it would be less efficient, so you would be drawing more than an 80+ gold when your system is drawing the same amount. 

So you're saying that a gold-rated 600W PSU only draws 590W from the wall under max load? That makes little sense.

[wowotek]

7 hours ago, HKZeroFive said:

So you're saying that a gold-rated 600W PSU only draws 590W from the wall under max load? That makes little sense.

CMIIW. the efficiency rating would affect how much the PSU draw from the outlet Per maximum load. like for example 600W Gold could Deliver 590W and will Draw Very Close to 590W from positive side, maybe like 595W for delivering 590W. for bronze efficiency maybe it can deliver the same 590W but will consume more Power than Gold from positive side maybe like 600W for delivering 590W. am I right ?

[mariushm]

There's a lot of miss - information in this thread.

 

As I've explained in my previous post above, the efficiency of a power supply is not fixed, throughout its range of output the efficiency varies a bit, but for most power supplies it's correct to say the peak efficiency is somewhere around 50-60% of their maximum output they're designed for.

No matter how well designed the power supply is, the efficiency is not 100%, it will always draw a bit more power from the wall compared to the amount of power it's delivered to various components.

To make it less confusing to people, standards like "80 Plus" have been invented, to assure people that the power supply can reach or exceed an efficiency percentage at certain loads:

 

 

For example, a power supply rated for 80plus bronze, must be at least 82% efficient at 20% of its maximum output and 85% at 50% of its maximum output, while a 80plus Gold power supply must be at least 87% efficient at 20% and 90% at 50% respectively.

 

So if we have two 500w power supplies, one Bronze efficiency and one Gold efficiency, at 20% (one fifth) load it means the power supplies will deliver 100w to components, and at 50% load (one half), the power supplies will deliver 250w to components.

 

However, the bronze power supply will consume from the wall at least  100w * 100/82 = 122 watts at 20% load, and 250w * 100/85 = 294 watts at 50% load , while the Gold rated power supply will use less power from the wall, more or less 100w * 100/87 = 114 watts at 20% load and 250w * 100/90 = 278 watts at 50% load.

 

So as you can see there's 16 watts less power dissipated as heat between the two power supplies at 50% load, which means the Gold efficiency power supply heats less, so fans with lower rotation speed can be used because there's no need to move so much air through the power supply to keep it cool, which makes the power supply less noisy and the components inside cooler (and they'll last longer if they're cooler) and the buyer more happy.

 

A good brand power supply will be capable of providing all the watts specified on the label to components, efficiency of the power supply has nothing to do with how much the power supply can deliver to components.

Very cheap power supplies or no name ones often put fake labels on the power supplies promising more than what the power supplies are actually capable of, but this has nothing to do with efficiency, it has to do with manufacturer installing undersized components inside the power supply to save money.

 

So on a brand name power supply, if the power supply says it can output 450w on the 12v rails, you can be sure it can output at least 450w on the 12v rail. For extra safety and reliability, most brand name power supplies design their power supplies to be capable of outputting a bit more than what's written on the label, usually most brand name power supplies are capable of about 105 to 110% of their advertised output for short periods of time. 

 

Someone also stated in a previous post that a higher quality power supply can make the components in the computer use less power, compared to cheaper power supplies.

This is technically TRUE but the differences in power consumption are so ridiculously small that it's just more convenient to say it's not true, that it makes no difference.

 

Here's a very simple explanation. Power hungry components in the computer, like video cards or processors, work with very low voltages, something like 0.8v .. 1.2v but with lots of current, up to 100-150 amps.

Because the power supply in your computer only provides 3.3v, 5v and 12v, these power hungry components have DC-DC converters on board to take a high voltage like 12v and convert it to the low voltage required. Naturally, as with any conversion, there are some losses in this process, but they're usually very small because these DC-DC regulators are very well optimized, custom made for the video card.

For example, since engineers know the power supplies will give them 12v, the circuit is optimized for 12v and may be up to 97% efficient if the input voltage is exactly 12v when the video card uses 100 watts of power.

However, if the input voltage is not quite 12v, let's say you have a bronze rated power supply that outputs only 11.8v when the video card uses 100 watts of power, that circuit on the video card may only be 96.8% efficient.

So basically, you're looking at 100w * 100/96.8 = 103.09 watts for a power supply that outputs exactly 12v, or 100w * 100/96.8 = 103.30 watts  , which means the video card may use 0.2 watts more with a less quality power supply.

This is basically NOTHING, it's noise, and that's the reason why everyone simply says components will use the same amount of power no matter what power supply you have.

 

 

[HKZeroFive]

15 minutes ago, wowotek said:

CMIIW. the efficiency rating would affect how much the PSU draw from the outlet Per maximum load. like for example 600W Gold could Deliver 590W and will Draw Very Close to 590W from positive side, maybe like 595W for delivering 590W. for bronze efficiency maybe it can deliver the same 590W but will consume more Power than Gold from positive side maybe like 600W for delivering 590W. am I right ?

You're right. Less efficient power supplies draw more power from the wall so you're correct in saying that a gold-rated power supply will draw less power from the wall than a bronze-rated one.

 

I have difficulty in understanding Trav's post because two of his paragraphs are contradictory.