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1) WHat is the wattage after the calculation of the PSU calculator, such as this one? Is it the wattage I know to buy for my pc? If it said 450W, and I buy a less efficient, cheap PSU of 450W, which doesn't provide a continuous power of 450W, is it bad?

2) What if I don't understand all the technical terms on the PSU calculator page?

3) Which online PSU calculator is easy to use and accurate?

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What terms don't you understand exactly? – MBraedley May 31 '11 at 2:08
The complete list in the section "PCI cards", and the following two. – lamwaiman1988 May 31 '11 at 2:14

The wattage from such a PSU calculator is intended to give an estimate of the PSU capacity that will be needed. The true goal is to install a properly sized PSU, neither undersized or oversized. But typically the number is an overestimate, probably for the simple reasons that overestimating is less harmful than installing an undersized power supply, heat reduces the PSU's capabilities and manufacturers tend to inflate and/or round-up the output specs. Unless you're gaming or doing something extreme like calculating prime numbers, then your PC is not likely to ever require or consume the calculated wattage. I see no problem with a "cheap" PSU, but I would never purchase a low quality PSU, assuming you understand the distinction. Note that a typical desktop PC only needs about a 250-300 watt PSU, which is what you find installed in most mass-marketed pre-built PCs.

If you can answer most of the questions for the calculator, then you should be able to obtain a reasonable number. Even I'm not sure what all the terms are, such as what "cold cathodes" refers to!

Easy to use (i.e. simple) and accurate are probably mutually exclusive attributes.

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cold cathodes are used for case lighting if you want one of those insane tricked out case – Journeyman Geek May 31 '11 at 6:34
Cheap and inexpensive carry different connotations. Cheap is low in quality, as well as being low in price; Inexpensive is just low in price. I would buy an inexpensive PSU, I would never buy (or recommend) a cheap PSU. – MBraedley May 31 '11 at 10:55

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