# How many watts

Discussion in 'Nvidia' started by Mr. Porter, Apr 11, 2007.

1. ### Mr. PorterGuest

How many watts of heat do 8800 GTXs put out on general

do they tell us this stuff?

Mr. Porter, Apr 11, 2007

2. ### Phil WeldonGuest

_____

The heat generated is equal to the electrical power consumed.

For one 8800 GTX at standard speed, 145 Watts peak electrical power in, 145
Watts peak heat out.
See http://www.xbitlabs.com/articles/video/display/gf8800_11.html .

Phil Weldon

Phil Weldon, Apr 11, 2007

3. ### SoCalCommieGuest

Nonsense! All the power isn't wasted (heat is waste), some of it does
usefull work (~60%). It's not an incandescent light bulb or a space heater.

SoCalCommie

"Behind every great fortune is a crime." - Honore de Balzac

SoCalCommie, Apr 11, 2007
4. ### Phil WeldonGuest

'SoCalCommie', falling into idealism, and failing to seek knowledge from
practice, wrote:
| Nonsense! All the power isn't wasted (heat is waste), some of it does
| useful work (~60%). It's not an incandescent light bulb or a space heater.
_____

The 'useful work' in this case amounts to milliwatts.
The rest is heat. Should you doubt this, try pumping 90 Watts through a
monitor video in connector.

Phil Weldon

Phil Weldon, Apr 11, 2007
5. ### PaulGuest

If 145W of electricity goes into the case, it all comes back as
heat. Think "conservation of energy". Think like an accountant
and balance the books. If it doesn't leave as heat, where did
it go ? I see no additional kinetic or potential energy here.
So it all left as heat.

Paul

Paul, Apr 11, 2007
6. ### Grant EdwardsGuest

Where is that work performed? If that 87W is not turning into heat,
it is being stored somewhere. Where is it being stored?
Unless you're claiming that there's 87W of power coming out of
the video connector, you're going to have to explain where it's
going.

Yup, except for a very small percentage that's being dissipated
in the video cable or the monitor's receivers.

Grant Edwards, Apr 11, 2007
7. ### Grant EdwardsGuest

Well a few milliwatts are proably transferred to the monitor
via the video cable.

Grant Edwards, Apr 11, 2007
8. ### First of OneGuest

Well, if you are going to count that, then include the few watts used to
drive the cooling fan.

First of One, Apr 12, 2007
9. ### Mr. PorterGuest

I water cool my video cards, soon, when the price drops I'll be water
cooling a couple of 8800GTX's

knowing 145, gives me a number I can get my system to dissipate. x2 + 65
for 345 watts

Mr. Porter, Apr 12, 2007
10. ### Grant EdwardsGuest

Those watts turn into heat as well.

Grant Edwards, Apr 12, 2007
11. ### First of OneGuest

Err, nope. Those watts are used to spin the fan blades. (Duh! Electric
motor.) A tiny amount is lost as heat in the form of bearing friction.

First of One, Apr 13, 2007
12. ### Phil WeldonGuest

'Mr. Porter' wrote:
|
| I water cool my video cards, soon, when the price drops I'll be water
| cooling a couple of 8800GTX's
|
| knowing 145, gives me a number I can get my system to dissipate. x2 + 65
| for 345 watts
_____

I have a web page that hasn't been updated since before the Pentium 4, but
it does include numbers useful for calculating cooling system capacity (I'm
not even sure it CAN be updated - my ISP seems to no longer support this
feature.)

See http://home.mindspring.com/~pweldon/ .

Phil Weldon

|
| I water cool my video cards, soon, when the price drops I'll be water
| cooling a couple of 8800GTX's
|
| knowing 145, gives me a number I can get my system to dissipate. x2 + 65
| for 345 watts
|
|
|
|
|
| | > How many watts of heat do 8800 GTXs put out on general
| >
| > do they tell us this stuff?
| >
|
|

Phil Weldon, Apr 13, 2007
13. ### Grant EdwardsGuest

And that all of that kinetic energy ends up as heat.
Everything that's not stored as potential energy ends up as
heat. That's simple thermodynamics. There's resistive loss in
the motor, heat loss in the bearings, and shoving the air
around heats it up.

100.00% of the energy consumed by a fan turns into heat.

You're not allowed to destroy energy. You can convert it into
mass, but that takes something like a particle collider -- not
a fan on a video card.

Grant Edwards, Apr 13, 2007
14. ### First of OneGuest

Remember the fan isn't just there to stir up the air, it actually propels
the air through a heat sink and out the back of the PC. The heat sink causes
a pressure drop due to aerodynamic drag. Volumetric flow rate x pressure
drop = power.

Sure, the air eventually slows down, but then the heat is generated outside
of the PC. The few milliwatts transfered to the monitor via the video cable
eventually turn into heat as well. Hence the need to define your control
volume.

First of One, Apr 14, 2007
15. ### Grant EdwardsGuest

For some cards that's true. For others, it just stirs up the
air.
It wold be interesting to know how much of he power dissipated
by the fan actually ends up as kinetic energy in the air.
Unfortunately my fluid dynamics skills are pretty weak.

Grant Edwards, Apr 14, 2007
16. ### GMANGuest

There is a power supply calculator here

http://www.journeysystems.com/?powercalc

GMAN, Apr 18, 2007
17. ### Mr.E Solved!Guest

Mr.E Solved!, Apr 18, 2007