Reason to not go big?

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HoppyChris

Limp Gawd
Joined
Jan 23, 2008
Messages
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So I'm in the early-planning for a build -- is there any reason to not go a little large on a power supply? I'm a bit fuzzy on the efficiency ratings -- if I have an 800 watt power supply, but only ever pull 200 watts to power the computer, the electricity consumption should be the same as if I had a 220 watt power supply? And put out the same amount of heat/noise as well?
 
The biggest reason (and really the only major one that matters) to not go big is the cost. If efficiency is the same at the same load level, then power consumption and heat put out is the same. Noise level depends on the fan used, the environment the power supply is used in, and how effective the power supply's cooling system is.

For most power supplies, efficiency drops off really quick below 20% load. For example, a 500 watt 80+ power supply might be 80% efficient at 100 watts load, but a 1000 watt 80+ power supply might be 70% efficient at 100 watts load.
 
HoppyChris said:
I'm a bit fuzzy on the efficiency ratings -- if I have an 800 watt power supply, but only ever pull 200 watts to power the computer, the electricity consumption should be the same as if I had a 220 watt power supply? And put out the same amount of heat/noise as well?
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Yes, because if the 800W put out 800W in that scenario, stuff would get really, really hot, literally like a toaster (2-slice)
 
HoppyChris said:
So I'm in the early-planning for a build -- is there any reason to not go a little large on a power supply? I'm a bit fuzzy on the efficiency ratings -- if I have an 800 watt power supply, but only ever pull 200 watts to power the computer, the electricity consumption should be the same as if I had a 220 watt power supply? And put out the same amount of heat/noise as well?
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Your efficiency tends to be pretty bad under about 30% load, as another poster said. 50-80% is sort of the sweet spot for efficiency.
 
It really also depends on the power supply. I believe the AX1200 is really efficient even at less than 10%. But just get like a 650-750w(even that is overkill) if you are only using a single GPU.

I got a 750W just because I like some extra power and it was the lowest PSU in the silverstone gold evolution series.
 
The AX1200 has ~84% efficiency at 10% load, compared to its efficiency curve of 88-92% for 20-100% load. While not bad, it still demonstrates the hit in efficiency if the load levels are too low.
 
BIG doesn't mean efficient.

Can't go wrong with high efficiency.

If your max load is going to be 750W under full load then it makes perfect sense to get a Platinum 850W PSU.

Between 10-20% above max power draw is a good number with 90% efficiency PSU.

Spending more money on higher than that doesn't make any sense since you will more than likely be paying more money.
 
Tsumi said:
The AX1200 has ~84% efficiency at 10% load, compared to its efficiency curve of 88-92% for 20-100% load. While not bad, it still demonstrates the hit in efficiency if the load levels are too low.
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That is still quite impressive for a 1200 watt PSU. Although if you ever run that at 10% you really need to stop buying PC parts. 120watts..on a 1200w PSU, oh lawd :p
 
xIronCrossx said:
That is still quite impressive for a 1200 watt PSU. Although if you ever run that at 10% you really need to stop buying PC parts. 120watts..on a 1200w PSU, oh lawd :p
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Computer at idle? The difference is minimal really, going from 84% efficiency to 88% efficiency when pulling 120W is like 6W. Efficiency numbers at load have a much bigger impact on your electricity bill.
 
Price? But yeah larger is better, because if your'e using 300w. It'd be more efficient to use 300w on a 1200w psu, rather than 300w on a 600w psu.
 
EliteGeek91 said:
Price? But yeah larger is better, because if your'e using 300w. It'd be more efficient to use 300w on a 1200w psu, rather than 300w on a 600w psu.
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That really depends on the PSU...for a price of most 80+ Bronze 1200w PSUs you can easily get an 80+ Gold and even Platinum 650W, and 50% load is usually more efficient than 25% load.
 
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