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a question about electricity consumption

W

wayne

2[H]4U
Joined
Aug 4, 2003
Messages
2,726
my power supply is 300w.... does that means its constantly drawing 300w from the wall socket but doesnt HAVE to USE it on computer components OR is 300w its limit?

lets say my computer truly draws 300w at all times.... and i have 110v on my house hold voltage... i divide 300w by 110 getting 2.72727272727 meaning i have almost 3 amperes

how do i kno how much it costs to leave it on for an hour?, a day?, a week?, a month, an year, a decade, a century, a millenium????.....


also, another question is is there some way to find the amount of current allowed for one electricity wall socket without checking on the circuit breaker?.... reason is because i may have a lanparty with like 5 of my friends so i have to check the circuit breaker in my basement which is currently blocked by this stupid huge shelf
 
no, it doesn't draw 300W continuously, that's just the max it's capable of.
depending on your system it may never draw close to that.

wall outlets are usually on 20A breakers.
 
I was kind of curious as well, how much does it cost to run an average computer, that's on 18-24 hours a day for a full year? any one know this?
 
It all depends on the efficiency rating of your PSU. If it only had a 60% efficiency rating then it would actually be drawing 480 watts in order to put out 300w.

Your PSU isn't outputing 300w though unless your system needs it. If you only need 100w for your system thats all thats ever pulled.
 
Originally posted by wayne
also, another question is is there some way to find the amount of current allowed for one electricity wall socket without checking on the circuit breaker?.... reason is because i may have a lanparty with like 5 of my friends so i have to check the circuit breaker in my basement which is currently blocked by this stupid huge shelf
Click to expand...
Most household 110 VAC circuits are either 15 or 20 amp, with 20s usually found in the kitchen and garage. I'd figure each PC drawing 4 amps (to be safe) so for 6 people gaming at once, you'll want to pull your juice from two different circuits.
 
Isn't the 300watt rating on the DC side of the PS?

I can't see my PC drawing 4amps on the A/C side, that would be about 480watts. I've got a watt meter and I was going to see how much my 4 machines pull, but just haven't had the chance to power down the systems.
I did measure my sisters 32" Sony Wega TV and it pulls 150watts on a black screen and 180watts when the picture is mostly white.
 
The 300w rating on a PSU is the DC side. In order to find the A/C side you need to figure out how much input power the PSU actually has to have in order to convert 300w of output power. Thats where the efficiency rating comes in. Usually the good name brand PSU's have arond a 70% efficiency rating. So if you had a name brand Antec 300w PSU and 70% of the A/C power was being converted to DC then you would need to pull around 390w. If it was 60% then you would need to pull 420w.

I think i made a miscalculation earlier lol. Its 420w instead of 480w.
 
My boxen run headless.
But I recon on each useing around 250 watts.

So running 24/7 I'm useing around 36 Kwh per day.

Luck..........:D
 
No way a computer draws four amps. Maybe a quad xeon or something, but normal desktops don't draw that much, even with a 17" crt. I ran my computer and my monitor through an ammeter a while back, and I believe it drew 2-3 amps. Not much at all. Like nearly all electrical devices, a computer will only draw as much current as it needs. It doesn't take in as much as it can and then throw away what it doesn't need. As far as how much it costs, you will have to measure how much your computer actually draws and figure out how much electricity costs for you and do the math.

Most residential circuits are 15 amps, some circuits are 20. You'll have to keep in mind which outlets are on which circuits. Often all the outlets in a room are on a circuit, and maybe an outlet in the hallway or something. Easiest way to tell which outlets are on which circuits is to start flipping of circuit breakers and seeing what goes off. I guess that doesn't help much if you can't get to the breaker box. It seems kinda pointless to even have a breaker box if you can't access it.

edit: I get the feeling the hardforums is straining to take a shit. I can't even access my cp now.
 
As stated it wont pull anymore power than needed, plus around 30-40% more due to the loss of power (efficiency) from the 120 VAC to 12/5/3 VDC conversion. A majority of computers dont use nearly as much power as people think, my Athlon XP2800, 2x 512MB PC3200, Radeon 9800 Pro, etc only draws 230 watts AC, ~ 2 amps, which would mean it's using less than 175 watts DC on the internal side of the computer. With average electricity prices of .10 per KWH, and a computer consuming 300 watts AC, it would cost around $20 a month to run it 24/7.
 
For a lan party you guys are all forgetting about a monitor. It draws power too.
What about speakers?? hopefully using headphones I guess.
 
Well, you asked for the costs of using your computer. If I assume that your computer on averarage uses 300W + 50W for the monitor and 100W for the speakers, you consume a total of 450W (= 0.45KW)

If you use your computer 8h / day you use 3,6kWh. (8*0,45). In Sweden 1 kWh costs roughly 10 Cent, i have no idea of the price in the US. This means that it costs you $0,36 / day, or $2,52 / week, or about $10,8 / month to use your computer.
 
I tossed out the 4A figure since they're also going to be using monitors. An average LCD is around 75-100 Watts and a 21" CRT is a good 150 Watts or more. Add to that the load on the PSU you'll get when playing games (higher than when surfing, to be sure) and 4 Amps is a SAFE bet, though not necessarily an accurate guess. I just added in some headroom so the guy doesn't have any problems with his small LAN party, that's all. The thing is, I personally would not want to run all 6 PCs (7 if they use a separate server) in a gaming session on one 15A circuit. :)
 
some friends who are organising a major lan party actually measured a PC & monitor, as the venue only has a 220A ring main.
They found that a high end machine (xp3200, r9800, watercooling, lots of harddrives) when loaded (gaming, 3dmark, prime95) drew less than 1 amp, and a large 19" CRT drew less than 0.5 Amps. I shall try and get a more accurate figure, as im just drawing off my memory at the moment.

Either way, it has been decided that the power supply can take 175 people at this forthcoming lan :D
 
Originally posted by ToiIetDuck
some friends who are organising a major lan party actually measured a PC & monitor, as the venue only has a 220A ring main.
They found that a high end machine (xp3200, r9800, watercooling, lots of harddrives) when loaded (gaming, 3dmark, prime95) drew less than 1 amp, and a large 19" CRT drew less than 0.5 Amps. I shall try and get a more accurate figure, as im just drawing off my memory at the moment.

Either way, it has been decided that the power supply can take 175 people at this forthcoming lan :D
Click to expand...
r u serious, can u get more information on the less than 1amp for that kinda computers?


you will have to measure how much your computer actually draws and figure out how much electricity costs for you and do the math.
Click to expand...
how?...
 
Originally posted by wayne

how?...
Click to expand...
With an ammeter. You will have to put the ammeter in series with one of the legs of 120VAC that goes into your power supply. Radio Shack has a clamp ammeter that plugs into a regular multimeter. It just goes around the wire so you don't have to splice into the wire. I think there is also a device called the Kill A Watt or something like that. You just plug it in and then you plug in your device and it tells you the current draw.
 
I have this Sencore Power Monitor to measure wattage use.

sencore.jpg


I'll be measuring my system when I decide to power it down,
desk-3-2004.jpg
 
Well, I don't know how ultimately accurate it is, but my UPS will tell me the current draw on it (for the outlets on the battery backup).

As I speak its at 275 watts with the system effectively idling. The equipment hooked up to this consists of the second computer in my sig, and the 19" CRT and 19" LCD in my sig. I just turned on my Firewire hard drive and it went up to 292 (drive is now idling, was at 297 while it started up). It's jumping around now between 290 and just over 300 as I use the drive off and on.

Anyway...

When I game with all these on I've never seen it exceed about 370 watts.

Thought it was worth noting.
 
If you are looking to figure the cost of an average system to run monthly then i'd have to say $15. I have a small store i rent where i have had up till recently been running 4 computers 24/7 SETI. I almost never use the lights and there is nothing else plugged into the outlets there. My electric usuage was averaging around $60 a month. The systems all have 350W psu's and one 19" monitor.
 
My PC.Monitor,Speakers, modem, router (I pluged the whole strip into it) useses 225 Watts. I plugged it into this kill a watt thing I got at radio shack
 
Originally posted by Format _C:
My PC.Monitor,Speakers, modem, router (I pluged the whole strip into it) useses 225 Watts. I plugged it into this kill a watt thing I got at radio shack
Click to expand...

Doesn't sound like my APC is lying to me then. :)
 
just to clarity, the measurement my m8 got was "1.5 amps for very high specced machine and monitor", and "0.8 amps for a pretty high spec machine - P4 1.8, 4 HDDs, GF4 ti4400, dvd & cdrw drives, 19" monitor"
 
My monitor runs at 170 watts.
Sony FW900.
Dont take it to lans as it weighs 42 Kg.
Bit hard to move one handed.

Luck.........:D
 
Originally posted by ToiIetDuck
just to clarity, the measurement my m8 got was "1.5 amps for very high specced machine and monitor", and "0.8 amps for a pretty high spec machine - P4 1.8, 4 HDDs, GF4 ti4400, dvd & cdrw drives, 19" monitor"
Click to expand...

You are running 220VAC (I think the UK is 220), so when converted to 110 (or 117) it's actually 3 amps and 1.6 amps.
 
Originally posted by wayne
is one amp off a dc voltages the same as one amp off ac voltages?
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Yes and No. Amperage is merely the messure of the current passing through the line, so you are messuring the same thing for both DC and AC. However, when you are converting from AC to DC there is always a percentage of power lost in the convertion process. To produce 1 amp of DC power, it may take 1.2 amps of AC power on the other side of the converter.

Just as a side note, dividing watts by voltage is not your true amperage. You also have to divide by a power factor (generally assumed to be .7) to get your actually amperage used. Right know my UPS is reading 610 watts, but is using 700 VA. My actually amperage usage is 700/120 or 5.8 amps. Thats with two comps and two monitors.
 
Originally posted by WS6
You are running 220VAC (I think the UK is 220), so when converted to 110 (or 117) it's actually 3 amps and 1.6 amps.
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good point :eek:

we're really 240VAC in the UK, so amps are going to be different as you said.
 
Originally posted by DDogbert
Yes and No. Amperage is merely the messure of the current passing through the line, so you are messuring the same thing for both DC and AC. However, when you are converting from AC to DC there is always a percentage of power lost in the convertion process. To produce 1 amp of DC power, it may take 1.2 amps of AC power on the other side of the converter.
Click to expand...

I think that is true when you aren't stepping the voltage down.
When you drop from 120VAC to 12DC, you'll have more DC amps available from less AC amps. 120VAC @.25amps can produce 12VDC @ 1.2amps
 
Originally posted by WS6
I think that is true when you aren't stepping the voltage down.
When you drop from 120VAC to 12DC, you'll have more DC amps available from less AC amps. 120VAC @.25amps can produce 12VDC @ 1.2amps
Click to expand...

Watts= voltage X amps Wouldn't it be 12v@2.5amps?
 
Originally posted by Bitchnmoan
Most household 110 VAC circuits are either 15 or 20 amp, with 20s usually found in the kitchen and garage. I'd figure each PC drawing 4 amps (to be safe) so for 6 people gaming at once, you'll want to pull your juice from two different circuits.
Click to expand...

Also consider that the 15 amp rating of the 120 volt branch circut in your room is only rated at 12 amps for continous flow. If you pull 15 amps constantly on a 15 amp circut, the breaker will eventually kick. Kick=dark room and upset lan party.
 
Originally posted by Disarray
Also consider that the 15 amp rating of the 120 volt branch circut in your room is only rated at 12 amps for continous flow. If you pull 15 amps constantly on a 15 amp circut, the breaker will eventually kick. Kick=dark room and upset lan party.
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Yes thats true
NEC Code is 80% of rated circut capicity. for continious loads
EX: 14 Amp washer will have to be on a 20 amp circuit
PC don't count as a fixed load though.
I have a 15 Amp circuit in my room 2PC a tv stereo. I can plug my heat gun to shrink my heat shrink tubing it works as long as I don;t leave it on for more than 5 mins. or elese dark room:D
 
Originally posted by Tigerbiten
My monitor runs at 170 watts.
Sony FW900.
Click to expand...

Sony FW900? As in, like, 24 inchs of 16:10 aspect ratio CRT goodness? *drool* :D
 
Originally posted by punisher
Watts= voltage X amps Wouldn't it be 12v@2.5amps?
Click to expand...

Well, I guess it would if there was no power loss from heat.
It looks like it loses 15watts from heat dissapation from the transformer.
 
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