Choosing the Right Power Supply Unit

AnandTech gives us answers on how much power a computer system actually requires. To test the power consumption and efficiency required from PSUs, they built 3 systems - Entry-Level, Midrange, and High-End.

Specs and Power Consumption:

1. Entry-Level System
2. • Intel Core 2 Duo E4500, 4GB Memory, P35 chipset motherboard, ATI Radeon HD 3650, an optical drive, and one hard drive
   • 90W at idle, and 140W at full load
3. Midrange System
4. • AMD Phenom X4 9850 BE, 4GB Memory, AMD 790X Chipset, ATI Radeon HD 3870X2, an optical drive, and two hard drives
   • 168W at idle, and 341w at full load
5. High-End System
6. • Intel Core 2 Extreme QX6850, 4GB Memory, NVIDIA 780i Chipset, NVIDIA GeForce 8800 Ultra SLI, an optical drive, and four hard drives
   • 310W at idle, and 544W at full load

For the Entry-Level system, the most efficient PSU was the Thermaltake TR2 QFan (300W). For the Midrange system, the Corsair VX450W (450W) was capable of supplying power, although the Enermax Pro82+ (625W) was the most efficient and silent. Going to the High-End system, the Antec Signature (850W) and the Zalman ZM850HP (850W) were the most efficient, and also the most quiet. It's nice to note that the Enermax Pro82+ (625W) was still capable in supporting the High-End system, although not as efficient as the two.

Another important thing to consider is the connectors available with the PSU, more particularly the PEG connectors for the graphics cards.

" Our three sample systems show that few if any people actually need anything more than 850W power supply, especially if you can get an appropriate number of connectors . About the only reason you should consider anything more is if you want to keep your power supply at a lower load, since optimal efficiency and lower noise levels usually come at around half the rated output. Overclockers might also want a bit of extra headroom. Otherwise, there's really no need for a 1000W power supply, and certainly not those with even higher ratings." [AnandTech | Debunking Power Supply Myths]

As seen with the tests, these are safe bets for PSU ratings:

• Entry-Level: 300W
• Midrange: 500W
• High-End: 700W

Probably a nice 700W PSU is a good choice for a system that you plan to get scheduled upgrades, until it reaches that High-End status. Other than that, a quality 500-watter is enough for a system with a quad-core CPU, dual-GPUs, and 2 HDDs.

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