plareta Posted September 27, 2008 Share Posted September 27, 2008 Hi, I have bought a Corsair TX750W CMPSU-750TX. So it's a 750w unit, but as it has "80% efficiency rating", I'm wondering which of these 2 statements is correct (in the case of 100% load) : Statement "A" : Measured power usage at the wall outlet is 750w. Internal computer components receive 600w (which is 750*0.8) Statement "B" : Measured power usage at the wall outlet is 937w (which is 750/0.8) Internal computer components receive 750w. So, in the case of a TX750W, which statement is correct ? Thanks ! Link to comment Share on other sites More sharing options...
Wired Posted September 27, 2008 Share Posted September 27, 2008 Power Supply Rated Wattage / Efficiency = Wall Load Link to comment Share on other sites More sharing options...
OldGeezer Posted September 27, 2008 Share Posted September 27, 2008 Statement B. The power supply will deliver 750 watts to the computer, but will take 937 watts from the wall in doing so. This begs another question: How much wall power will be required to deliver 400 watts to the computer, using this same power supply? Efficiency is at a rated load. I propose that efficiency goes down as the load on the power supply decreases. 1000 watts is a LOT of power. How many computers really need more than 400 watts? Very few, I suspect. Use the power supply recommender on the Corsair product page and see what they really recommend. Bigger is not always better. Link to comment Share on other sites More sharing options...
plareta Posted September 27, 2008 Author Share Posted September 27, 2008 Thanks for your answers ! Use the power supply recommender on the Corsair product page and see what they really recommend. Bigger is not always better. I have a Core 2 Quad Q9650 and a huge graphics card (GTX 280) which is known to need a lot more than every auto-recommender can tell (some people have tried using 550W or 650W with that card, without success) Statement B. The power supply will deliver 750 watts to the computer, but will take 937 watts from the wall in doing so. Wow ! That means if I want to buy a battery back up power unit, I will need a big one (even the 865 Watts/1500 VA is not enough). Link to comment Share on other sites More sharing options...
Wired Posted September 27, 2008 Share Posted September 27, 2008 How much wall power will be required to deliver 400 watts to the computer, using this same power supply? Efficiency is at a rated load.Check Corsair's website for the bell curve for efficiency for each power supply. Link to comment Share on other sites More sharing options...
OldGeezer Posted September 27, 2008 Share Posted September 27, 2008 Thanks for your answers ! I have a Core 2 Quad Q9650 and a huge graphics card (GTX 280) which is known to need a lot more than every auto-recommender can tell (some people have tried using 550W or 650W with that card, without success) Wow ! That means if I want to buy a battery back up power unit, I will need a big one (even the 865 Watts/1500 VA is not enough). I don't think it is that drastic. You need to check the current draw at the wall and multiply that times your wall voltage to know just how much power your computer is drawing. I'm an electronics tech by trade. I have the equipment to accurately do this. I doubt that you do. In any event, I would bet your computer needs are under 500 watts. Take a look at my system specs. Corsair recommended 450 watts for mine. ATI recommended a 350 watt supply with the single 3870 video card and system I'm using. I'm using a 650 watt supply because Fry's made me a deal I couldn't refuse on my Thermaltake. I had a 300 watt before I bought the 650. I went to Fry's looking for a 450 watt supply only because I intended to upgrade the video card. Also, motherboards and the newest CPUs are much more efficient than those of even 3 years ago. Another way to look at it is: Even 300 watts of waste is a lot of power. It will make your electric company happy to see you buying that from them. 300 watts will also dump considerable heat into the room. Link to comment Share on other sites More sharing options...
plareta Posted September 28, 2008 Author Share Posted September 28, 2008 Another way to look at it is: Even 300 watts of waste is a lot of power. It will make your electric company happy to see you buying that from them. 300 watts will also dump considerable heat into the room. Well, maybe I'm wrong, but I think the PSU only draws from the wall what the computer draws from the PSU (divided by 0.80 efficiency). So, if I buy a 1000w PSU, and my computer only needs 400w, the PSU will not consume 1000w, it will consume 500w (400 / 0.80). The only waste here is the price of a bigger-than-enough PSU. But I don't think it will consume more power or produce more heat. Link to comment Share on other sites More sharing options...
HRAW Posted September 28, 2008 Share Posted September 28, 2008 Your power supply will only draw from your wall outlet what it's needed to power your PC plus the difference related to the efficiency rating. If your PC consumes 283 Watts and the PSU Efficiency for the 283 Watts level is equal to 80%, Your PSU will draw from the wall outlet a total of 375.75watts= 283/0.80= 353.75 Watts. 1º - If your PC consumes 283 Watts/hour with an efficiency of 80 and you live your PC on for about 6 hours a day, it will consume daily 353.75 Watts X 6 Hours a Day = 2.122 kWh a day. Now if you live It on every day for 6 hours during a year, it will consume annually a total: 2,122 kWh X 365= 774.53 kWh annually, being 80% to run your PC and 20% as a type of waist. 2º - Now, let’s take a look at costs: If your local company charges you $0, 20 cents for each KWh you consume, your power supply will make you spend about US$154, 91 a year to run your PC (US$0, 20 X 774.53KWh), being US$123.61 what your PC really used and US$31.30 that was in some way wasted by the Power Supply to be able to make your PC run. Now, if you will keep Your PSU for at least the next 5 years, this PSU will cost you more US$156.50 on excess of power consumption for the same period. So be careful when you buy your PSU, sometimes due to efficiency your initial savings will go down the drain. So, in my opinion when we are pricing parts to build a PC we always need to buy the best PSU your money at the time or your overall financial conditions will permit you. Somehow, the PSU is equal to a heart on a human body, if it is no good, it will not matter much what type of brain you have, for sure sooner or later the heart will fail and take that nice brain, legs, arms and etc. with him.:mad::o::(::eek::mad::evil: Link to comment Share on other sites More sharing options...
OldGeezer Posted September 28, 2008 Share Posted September 28, 2008 You both forget the efficiency curve. A 1000 watt power supply may be 80% efficient at say... 900 watts. But at 500 watts that same power supply might only be 65% efficient. Link to comment Share on other sites More sharing options...
HRAW Posted September 28, 2008 Share Posted September 28, 2008 You both forget the efficiency curve. A 1000 watt power supply may be 80% efficient at say... 900 watts. But at 500 watts that same power supply might only be 65% efficient. Dear Friend, Sorry to say, but we have to base our information on facts and to do so we have test by ourselves and also if possible do some research. In our days the internet is a source to answer any question. You will only have to search and them filter the information that you found by crossing it, by doing so you will probably find your answer. In following the above procedure, you will be able to be very helpful to others when they ask you a question by given a correct answer or helping them to find it by themselves. So, when I decided to purchase the HX 1000, I did some research, if you want to answer some of your questions, just visit the following links: http://enthusiast.hardocp.com/article.html?art=MTQ4NywxLCxoZW50aHVzaWFzdA== http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/6951-corsair-hx1000w-power-supply-review.html http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=89 Now Talking about the HX1000 efficiency, according to tests the following holds truth according to JonnyGuru and others. The efficiency of the HX 1000 is as Follow: Results from Corsair HX1000 COLD load tests: DC Watts= 215W AC Watts= 262W Efficiency 82% DC Watts= 414W AC Watts= 484W Efficiency 86% DC Watts= 612W AC Watts= 719W Efficiency 85% DC Watts= 807W AC Watts= 960W Efficiency 84% DC Watts= 973W AC Watts= 1160W Efficiency 84% Results from Corsair HX1000 HOT load test: DC Watts= 215W AC Watts= 262W Efficiency 82% DC Watts= 414W AC Watts= 484W Efficiency 85% DC Watts= 612W AC Watts= 719W Efficiency 83% DC Watts= 807W AC Watts= 960W Efficiency 83% DC Watts= 965W AC Watts= 1191W Efficiency 81% If I am not wrong, a PSU to be able to receive a 80 Plus certification, cannot at any time run at 60% efficiency even for a fraction of a second in any wattage, probable the lower it can go is around 78% for a very specific situation e for a very short duration. I wish the above information can be of some help! Link to comment Share on other sites More sharing options...
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