power consumption question...

[Shiori]

Haha... my first thread in a very long time


Anyway, I just wanted to ask a quick question about how computers use up electricity and stuff... you see, I'm plugging my computer in a 220 volt outlet, and it's on almost 24/7 (due to this wonderful thing called torrents )... if I plug this in instead in a 110v power outlet, will it consume less electricity than plugging it in a 220v power outlet?

Sankyuu for help on this

[Phoenix]

I don't think so.

Power Consumption is the result of appliying the Watt Law, aka Power = Amps * Voltage, in general. So if the computer consumes exactly the same amps when conected to either outlet it will does consume less, but, I hardly think this will happen. If plugged to a 220V outlet it'll suck less amps than plugged to a 110V outlet. In a 110V outlet it'll suck more amps. So as the voltage is minor (110V) the amps consumption will be greater in order to "match" the watts your equipment needs regardless if plugged to a 220V or 110V outlet, in other words it will consume the same watts.

Once I measured my computer(no monitor included) consumed amps at full load and was about 2.4 Amps, it was plugged to a 120V outlet, doing the math, it consumes 2.4/120 = 288 Watts more less.

So in order to confirm what I said, you could measure the amps of your computer when plugged to a 220V outlet and the amps consumed when plugged to a 110V. You'll have different amps values but if you multiply each one by the correspondent voltage I can assure you to have the same wattage results.

[Celine]

Huh, it is possible to have different rated outlets (220/110) in the same building? I thought this was a region thing.

And you could fry your PSU putting it into the wrong rated outlet.

[Kazuya Mishima]

Originally Posted by Celine

Huh, it is possible to have different rated outlets (220/110) in the same building? I thought this was a region thing.

Atleast in Mexico you can. The normal is 110 but with air conditioners you need to set 220 in your house (and it will be used only for the AC) as it consumes more energy than the normal electronics. If you plug the AC to the the normal 110 all the lights in the house will pale and things may fry.

[james.miller]

that's probably because @ 110v to produce the same output the conditioner needs to draw more current than at 240v. Same for a psu. Lower voltage = higher current for the same amount of work. So possibly, no. it would actually be less efficiant because more current = more heat, if anything.

over-head power cables run at extremely high voltages because you can get away with using less current, and in this instance less current = loss energy loss due to heat, amongst other things.

[Zephon]

Heh. It's been a really long time, huh, Shiori? Anyway, I too haven't posted in a while.

Anyway, about the power consumption question. What Phoenix said is pretty much true, but I would like to add something. He forgot to mention the effects of inductance and capacitance in the power consumption. What Phoenix said about multiplying current and voltage is true for resistive circuits.

In a pure resistive circuit, all the elements have a resistance, and no capacitante/inductance. This way, all the power is dissipated (power given by current * voltage). But when there are inductors or capacitors, these components drain current too, but they don't really dissipate the energy (there is always a small resistance in the component that does this, but let's not get too deep), they accumulate the energy in electrostatic/electromagnetic energy form.

The REAL power consumed by your machine is due to the resistive part of the circuits only. When you directly multiply the line's voltage * current, you have what is called APPARENT power (given in volt-amperes VA, not watts W), which is usually a little bit higher than the real power.

In most residences in 110V areas, there is also a 220V plug. This is because there are 3 lines that come to your house. One is the ground (reference), taht is always 0V. The other is 110V alternate current (comparing to the reference), and the other is also 110V alternate current when compared to the reference. But both 110V lines have a 180° phase between each other (they are sinusoidal waves), and that makes the difference between them 220V. So the question about having 110V and 220V in the same house is answered by: yes, you can have both, you just need to choose the correct lines to use in your plug.

Ok, it was a little bit too technical. Maybe people who study (or are willing to study) electrical engineering will like it.

[Shiori]

I have to admit, I was lost in the whole electrical mumbo-jumbo ^^;; but I think I understand enough to understand that it really doesn't matter where I plug it in, it'll still consume the same amount of power and my elelctri bill will be more or less the same, is that right?

[Zephon]

Originally Posted by Shiori

I have to admit, I was lost in the whole electrical mumbo-jumbo ^^;; but I think I understand enough to understand that it really doesn't matter where I plug it in, it'll still consume the same amount of power and my elelctri bill will be more or less the same, is that right?

Exact. In fact, for computers, it is even less important whether you use 220V or 110V plug. That's because all the components in your PC use direct current, with much lower voltage than 110V. You probably know the PSU (Power Supply Unit) in your PC, right? Well, what it does exactly is to take the 220V/110V electricity, rectify (make from alternate current to direct current), and then lower the voltage to values usable by the computer (+5V, -5V, +12V and +3.3V), which later may be converted to other voltages for each component (for example, the processor uses something around 1.5V).

So, no matter if the input is 110V or 220V, it will be converted either way to the same lower voltage, so the computer can really use it.

[Shiori]

Hmm, so in that case it's not whether I plug it into a 110v or 220v outlet, but rather how much power does the PSU take. Makes much more sense now Hehe thanks Zephon

[Phoenix]

Originally Posted by Zephon

Anyway, about the power consumption question. What Phoenix said is pretty much true, but I would like to add something. He forgot to mention the effects of inductance and capacitance in the power consumption. What Phoenix said about multiplying current and voltage is true for resistive circuits.

Yeah, I messed up terms a bit

Originally Posted by Zephon

The REAL power consumed by your machine is due to the resistive part of the circuits only. When you directly multiply the line's voltage * current, you have what is called APPARENT power (given in volt-amperes VA, not watts W), which is usually a little bit higher than the real power.

Zephon, in this thread I tried to explain RZetlin his concern, so my question is: by measuring the VA consumed by each equipment(CPU, monitor, peripherals, etc., using the amps * voltage formula for each one), adding their individual resulting VA, would give a rough idea of total VA needed to be delivered by the UPS?

[Zephon]

Originally Posted by Phoenix

Zephon, in this thread I tried to explain RZetlin his concern, so my question is: by measuring the VA consumed by each equipment(CPU, monitor, peripherals, etc., using the amps * voltage formula for each one), adding their individual resulting VA, would give a rough idea of total VA needed to be delivered by the UPS?

Yes, I believe so. You can add all the values (as long as all of them are in VA), and estimate the VA needed by the UPS. But since this value varies along time (sometimes the computer consumes more, someetimes less, sometimes it's the real power that changes, sometimes it's the reactive power), you need to be careful not to measure everything exactly in a moment when the consumption is too low, otherwise your estimated value will be incoherent.

[Phoenix]

uhm, alright.

That's so true about those dynamic loads, and all the external factors that determine final consumption like harmonics, Power Factor, power quality, etc., fascinating indeed.

Thanks Zephon.