Original subtitles

In this lesson, we're going to talk

about wattage ratings.

Now every power supply has a wattage rating associated

with it.

When I talk about the wattage rating, I'm talking

about the power supply unit's output capacity or capability.

We measure this in Watts.

Now a typical standard desktop PC that you might use

in your office could use something like 200 or 300 Watts.

But if you have a machine

that has multiple internal hard discs, a very powerful

graphics card or something like a gaming PC

this could use anywhere from 500 to 900 Watts.

And so when you're picking

out the components for your system

you need to consider how much wattage they're going to draw.

And that way you can install the proper power supply

into that system.

Remember every device

inside your computer is going to require power

and it gets all that power from your power supply.

Therefore, if you have more devices inside the computer

such as a powerful processor or graphics card

or having multiple hard drives, CD ROMs, DVDs,

or other components, you're going to need

to have more power provided

in the form of wattage from your power supply.

Another thing to keep in mind is that if you bought a system

off the shelf, such as going to Best Buy

or Office Depot or another big box retailer like that

you have a system that was built

for a particular wattage in that power supply.

So if I got a standard desktop computer

and that had maybe a 250 or 300 Watt power supply in it

and I decided I wanted to upgrade that computer

by inserting a better graphics card

into a PCI Express x16 slot,

that might actually draw more power than

that power supply can provide.

That would be a big issue for me.

And so you have to be able to figure

out what is the wattage requirements

of your system either if you're building it

from scratch or doing a component upgrade.

To do this you need to determine the wattage

that's going to be required by adding all

of your devices together.

If the device is measured in Amps

you're going to have to convert that amperage into wattage.

And to do this, you use the calculation

of Amps times Voltage, which is usually written

as A times V or I times V because I stands

for current and amperage is a measure of current.

For example, I recently installed a new graphics card

into one of my systems.

This graphics card was a 6,700 XT Graphic Processing Unit.

Now that processing unit actually draws 230 Watts.

So if I was trying to put this

into a standard desktop computer that you use

in an office environment

and its entire power supply only supports 300 Watts,

well, it's not going to be able to support this graphics card

because 230 Watts is almost the entire power supply

capability just for this one card.

So in the system I was using,

I was using an 850 Watt power supply

because I was building a gaming PC.

And so out of 850 Watts total of the power supply

I could easily dedicate 230 Watts of that

to this graphics card.

So you may be wondering how much wattage does something

like a processor use?

Well, if you have a low power processor

it may use something as low as 17 Watts.

But if you have a high power processor like

that used in a gaming computer, it may use

up to 240 or 250 Watts of power.

Now a mid tier CPU will generally use

around 100 to 150 Watts.

When you look at your motherboard

most motherboards are going to use around 50 to 80 Watts.

If you have something like a CD or DVD drive

which we call an optical drive, these use around 30 Watts.

If you have a hard disc drive, these use around nine Watts

and if you have case fans, each of those case

fans will usually use around six Watts.

So as you're building a computer, you need to think

about all of this as you're adding it together

and figuring out what your total wattage is going to be.

For example, if I was going to build a gaming PC

that's going to have a standard motherboard,

a top tier processor, a nice graphical processing unit

as well as a hard drive,

an M2 SSD and about six case fans,

I can add all these things together

and figure out how much wattage I'm going to be using.

That would be 80 for the motherboard, 230

for the graphics card, another 250 for the processor,

another nine for the hard drive, nine for the SSD

and then six Watts for each of those six case fans.

This gives me a grand total

of about 614 Watts of power being required.

Now, would I go out and buy a 614 Watt power supply?

Well, no, for a couple of reasons.

One is there's not a power supply

that's going to be sold as 614 Watts

because normally they're sold in increments

of 50 or 100 Watts, such as a 250 Watt power supply

or a 500 Watt power supply or an 850 Watt power supply.

But in addition to that

you can't just use the minimum amount

of wattage that you calculated.

And this is because you may add additional components

into your system later.

And so if I bought the minimum amount

and I put something else in like an additional hard drive

I would now go above that amount

and that power supply can no longer support it.

So you always want to buy a power supply

that's a little bit bigger than what you calculate.

In the case of this system, where I calculate 614 Watts

I might want to buy something

like a 750 or 850 wat power supply

because that gives me additional overhead and room

for me to add additional components later on, if I need to

or if I upgrade the processor or graphics card

to a more powerful unit that requires more power later on.

Now, in addition to all of this

there's another power calculation you have to think about

and it's how much power is being drawn

out of your wall outlet.

Just because you bought a power supply

that supports 500 Watts or 850 Watts,

it doesn't mean that's the amount

of wattage that's actually being drawn by the system

when it comes from your wall outlet.

Instead, power supplies are not considered 100% efficient.

So for easy math

let's assume we bought a 500 Watt power supply

for a desktop computer system.

We plug it into the wall

and we want to calculate how much is being drawn

from that wall.

Well, it's not going to draw 500 Watts

because it's not 100% efficient.

If it was, we would get 500 Watts

of power from the wall that would translate

to 500 Watts of power for our system.

But instead, most power supplies are going to operate

around 70 or 75% efficient.

Or if you get a high quality Energy Star model

these can be 80% efficient.

Let's talk about a less efficient 70% model first.

If I have a 500 Watt power supply

and it's 70% efficient

that means we're actually going to be drawing around 714 Watts

of power from the outlet in order to create 500 Watts

of usable power for our computer within the power supply.

Now what happens to other 214 Watts of power

or 30% that we're losing?

Well, that's actually going to take the form of heat.

When we do the transformation

from high voltage AC to low voltage DC

a lot of that is lost in the form of heat,

and that's why these things are not 100% efficient.

Now, on the other hand, if I was using something

that was an 80% efficient power supply

I would take that same 500 Watt power supply

and divide it by 0.8 or 80% to get the amount

of wattage it would be.

And in this case, that would be 625 Watts.

So if I wanted to create 500 Watts

of power with an 80% efficient system, I can do

that drawing 625 Watts instead of having to draw 714 Watts

like I did with a 70% efficient system.

So you can see even with that 10% efficiency difference

by going to that more expensive and higher quality

Energy Star rated 80% compliant power supply,

I can now save almost 100 Watts

of power every time I'm turning that computer

on as I'm drawing power from the outlet.

And that's going to equate to savings

in your energy bill and power bill at the end

of the month as well, because you're drawing less power.

If you're a gamer and you're building a custom PC

this is something you need to keep in mind.

And it is worth spending a little more money

on a high efficiency power supply

because that's going to be able to save you money each

and every month when you're running that system.

Now I know I just threw a whole bunch of numbers

and math at you, and you may be wondering for the exam

do I need to be able to calculate these wattages

and these loads?

And the answer is no.

You need to understand the concept of the fact

that power supplies are not 100% efficient.

They're going to draw more power

than what they're going to be creating in the power supply.

And what you create in the power supply has to be enough

for all of the components you have.

The more components you have, the larger

the power supply you're going to need

and the bigger the power supply

the more power it's going to draw from your wall outlet

leading to higher energy bills.

If you're running a server farm

you want to have things that are as efficient as possible.

And the reason is these servers can suck up a lot of power.

And if you have less efficient systems

you're going to be paying more money every month

in your utility bills as a company.

And that's not going to be beneficial to you, especially

if you're having a system that you're going to be using

for the next three or five years.

So spend a little more money up front

and get a higher efficiency power supply

that will be able to save you money for the long term.