Power Consumption of a PSU

[thismafiaguy]

If I upgrade the 450W PSU of my system to an 850W PSU, what would be the impact on the power draw? Assuming I kept every other component the same and both power supplies have the same efficiency?

 

[smorizio]

The wattage used would be the same. Ps only going to give a system the amount of power that it draws. You have to add more parts or larger gpu for the wattage used to go up.

 

[Robert Pankiw]

@Smorizio, I'm not sure that's true. This is my interpretation:
Let's say you have a 450W 80+ Gold PSU now, and you want to look at getting an 900W 80+ Gold PSU.

If you system uses all 450W, then you'd be 87% efficient, meaning you'd draw about 517W from the wall.
If you went to 850W gold, with the same draw, you'd be 90% efficient, meaning you'd draw 500 W from the wall.

If you paid 40 cents / KWH (Which is a MASSIVE price, I pay about 11.8 cents/KWH on peak, about 6 cents on off hours) 17W is .68 cents per hour (yes, cents, not dollars) saved by going to the better PSU.

Of course, if you'd using an OEM PSU that isn't even 80+, and you go to an 80+ Gold, it would be a much bigger difference. The big benefit from going to 80+ isn't always the power savings, but knowing that it's quality components that give a PSU their rating. I don't want low end parts potentially damaging my system, so I went with a high end PSU, and would do it again. The wattage doesn't define the quality of the parts, however. At least, in general that's true. 😉 You can't get an 80+ Gold rating using garbage components though.

Wow I do ramble on and on, don't I?

 

[JackNaylorPE]

Well if you were drawing anything close to the 450 watts, actually the power consumption would go down. Two power supplies can have the same efficiency at their load percentage from being "Gold Rated" but PSU's hit peak efficiency at 50% load.....so lets say while gaming ya draw 400 watts.

http://en.wikipedia.org/wiki/80_PLUS

400 watts on a 450 Gold will be about 87.3% efficient so 458 watts outta the wall
400 watts on a 850 Gold will be about 89.7% efficient so 446 watts outta the wall

12 watts x 30 hours a week x 52 weeks = 18.72 kw-hrs x $0.10 = $1.87 per year

 

[thismafiaguy]

I'm sorry guys, I actually meant power draw from the wall. Not the amount of power consumed by the components.

But thanks for the replies! I think my question is answered