Power Supply VS Power Consumption

[anException]

This has been bugging me for a bit and would just like some clarity from the experts if possible, supposed you had the following two builds:

Build 1

Intel i3-6300
Intel B150 Type Motherboard
2 x 8 GB DDR4 (1.2v)
Samsung 750 Evo 250GB
1000W (80-Plus Platinum Level) (Modern PSU)

Build 2

Intel i3-6300
Intel B150 Type Motherboard
2 x 8 GB DDR4 (1.2v)
Samsung 750 Evo 250GB
500W (80-Plus Platinum Level) (Modern PSU)

Now obviously the power requirements for both builds will be very low and exactly the same. My question is, (and I know it might sound a bit silly to ask) but will the 1000W PSU cost you noticeably more per month to operate - in terms of pure electricity usage? Or are modern PSU's smart enough to only supply what is asked of it and therefore the monthly operating cost of the example systems would be roughly the same?

 

[pcgeek11]

They will both use the same amount of power. Power supplies have always been like this, it isn't something new.

Power in watts = Voltage X Current

 

[MongGrel]

If you are not planning on running a couple GPUS in SLI, a good 550 would probably cover that I imagine.

But there enough decent 650 etc out there at are rated nice.

1000 is serious overkill for most people.

 

[anException]

If you are not planning on running a couple GPUS in SLI, a good 550 would probably cover that I imagine.

But there enough decent 650 etc out there at are rated nice.

1000 is serious overkill for most people.

Thanks for you answer but I was merely illustrating this example to try and ask my question. This has nothing to do with a build I'm doing.

 

[anException]

They will both use the same amount of power. Power supplies have always been like this, it isn't something new.

Power in watts = Voltage X Current

Thanks for the answer, this is exactly what I wanted to understand.

 

[lehtv]

Theoretically, a bigger PSU will cost you more to run because it will run at a lower efficiency. 80 Plus certified units only need to pass the required efficiency numbers at 20%, 50% and 100% load (apart from 80+ Titanium for which 10% load also has a requirement). See wikipedia. Firstly this means that since there's no requirement for efficiency below 20%, different units with the same 80+ rating can have wildly different low load efficiencies. Some 80+ Gold units will do 80% at 10% load, others will plummet to 70%. Secondly, efficiency is typically best at around 50% load or a little above. So for a given build, the optimal PSU capacity is such that idling or low system load requires close to 20% of the PSU's capacity, while high system load requires about 50% or a little more. Typically though, 20% load at system idle is difficult to achieve because modern components have very good power saving features - you'd have to push load wattages to near 100% of the PSU's capacity which would make it run very hot and noisy and potentially reduce its lifespan.

However, the differences in actual watts spent are small enough that none of this matters in practice. You will make a much bigger impact on overall cost by
1) choosing a lower wattage unit because it is less expensive, not because it will run more efficiently
2) buying a less efficient unit - to offset the higher up front cost (of 80+ Gold over 80+ Bronze, for instance) with lower running costs, you will need a very beefy, high wattage build and actively use it for several years
3) buy parts that require less power in the first place
In that order.

 

[mnewsham]

It would depend on the specific model. The 1000w unit will not have been tested at under 20% load levels, and the majority of the time that computer will be pulling ~50-150w. Maybe 200w if something crazy happened. At that low level the 1000w unit MIGHT be terrible inefficient, since there is no 80+ spec guideline for 10% load levels and below on platinum rated PSUs you have no idea if the 1000w unit will be anywhere near as efficient as the platinum spec would have you think. MOST quality 1000w units wouldn't be too bad, but I have seen some go under 80% efficiency at ultra low power draw(which your proposed build would fall under).

So my vote would go for the smaller 500w unit every time.

Hell a 500w unit is more than enough for a GTX 1080 and whatever else you want.

 

[anException]

It would depend on the specific model. The 1000w unit will not have been tested at under 20% load levels, and the majority of the time that computer will be pulling ~50-150w. Maybe 200w if something crazy happened. At that low level the 1000w unit MIGHT be terrible inefficient, since there is no 80+ spec guideline for 10% load levels and below on platinum rated PSUs you have no idea if the 1000w unit will be anywhere near as efficient as the platinum spec would have you think. MOST quality 1000w units wouldn't be too bad, but I have seen some go under 80% efficiency at ultra low power draw(which your proposed build would fall under).

So my vote would go for the smaller 500w unit every time.

Hell a 500w unit is more than enough for a GTX 1080 and whatever else you want.

Thanks for the answer, I think I was not putting this out there clearly enough in my question, I raised this as a purely theoretical discussion topic. I used 500W and 1000W to have nice clean contrast for the discussion.

 

[UsandThem]

A nice basic article about this issue:

http://www.hardwaresecrets.com/understanding-the-80-plus-certification/

A more in-depth one:

A_Better_Way_to_Compare_PSU_Efficiency

Like mnewsham stated, it is dependent on the actual PSU.