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Thread ID: 65901	2006-02-03 21:47:00	PC Power Consumption	The_End_Of_Reality (334)	PC World Chat

Post ID	Timestamp	Content	User
426977	2006-02-03 21:47:00	This is not one of those 'this is what I am going to get what PSU will I need' This is one of these 'How much power does my PC consume at 240V AC?' Now, I have though about this and am not too sure, for example I would say mine consumes 250W idle *estemate* and possibley 450W full load *estemate* according to JSCustomPCs wattage calculator, didn't have exactly my spec, but I put the closest, but what sort of impact does that have on the 240V AC sockets? in terms of power consumed 12V DC is 1/20th of 240V AC, so would the socket consumption be 250W divided by 20 and that equals 12.5W at 240V AC and at full load, 450W divided by 20 equals 22.5W, this just doesn't sound right because the PSU has dual 12V rails that can supply 18A each, where does it get this 18A? Well there is the end of my short question :p Thanks for your replys :)	The_End_Of_Reality (334)
426978	2006-02-03 22:01:00	No, your calulations are mixing watts up with amps. A 60W bulb at 12V (in a perfect world) uses 60W at 240V, just less amps. IE, it uses 5A at 12V, but only 250mA at 240V. Watts = Volts * Amps. But power supplies aren't perfect, so the socket consumtion will be slightly MORE than the DC consumtion. So if the computer used 250W it would draw about 270-300W I suppose (just a guess really, Billy or someone will know more accurately).	george12 (7)
426979	2006-02-03 22:25:00	Oh, I see how it works, the voltage is dropped but the current is raised on the DC and the PSU still draws 250W (in a perfect world :rolleyes: ) from the socket to equate the voltage and current changes. But seeing as it is not a perfect world it needs to raise the current draw to counteract the heat and electrical polution of the conversion between 240V AC and 12V DC	The_End_Of_Reality (334)
426980	2006-02-04 00:27:00	Any power supply has an "efficiency". When using an inverter to produce 230V AC from "12V" batteries, I use 20X to roughly estimate the current drain from the battery. That's very approximate because the battery voltage drops in use .. from over 13V down to under 11V. But its a reasonable average for an inverter with en efficiency of about 85-90%. A PC power supply will probably be about 70-75% efficient. Efficiency costs money. The mains socket can supply lots of input power, and the fan can handle the heat the losses produce. ;)	Graham L (2)
426981	2006-02-04 04:35:00	But seeing as it is not a perfect world it needs to raise the current draw to counteract the heat and electrical polution of the conversion between 240V AC and 12V DC The difference in power (volts x amps) drawn from the 230 volt mains, and the power out at 12 volts, is due to conversion losses and relative efficiency, the difference generally being dissipated as heat. The figures will be closer together for a well designed and efficient power supply, but you needn't really think about it. Cheers Billy 8-{)	Billy T (70)
426982	2006-02-04 04:46:00	So basicly, what you guys are saying is that the PSU draws a little more power than what it is rated for?	The_End_Of_Reality (334)
426983	2006-02-04 04:54:00	Do you have a high voltage multi meter? It would surely tests the voltage, wattage, amperage of your PC...	Mr Wetzyl (362)
426984	2006-02-04 05:07:00	So basicly, what you guys are saying is that the PSU draws a little more power than what it is rated for? It depends on whether the supply is rated for its maximum power input or its maximum power output. Most electrical devices are rated for the power that they draw from the mains supply i.e. the maximum power input. Cheers Billy 8-{)	Billy T (70)
426985	2006-02-04 05:15:00	Do you have a high voltage multi meter? It would surely tests the voltage, wattage, amperage of your PC... Yet to see a standard multimeter that measures true "watts", but I do have a power analyser (kWh) here, my P4 2 GHz PC uses 140 - 180 watts average in normal use, monitor excluded. Certainly if would peak for a second or less at much higher watts, or would be a higher average if gaming. Just talking of normal "business use" here. Of course the actual VA of the 180 watts would be more in the order of 240 VA, but your electricity meter measures Watts, not VA.	godfather (25)
426986	2006-02-04 09:22:00	Do you have a high voltage multi meter? It would surely tests the voltage, wattage, amperage of your PC... No sort of Multimeter here :(	The_End_Of_Reality (334)
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