Efficiency: Pay Attention To The Power Supply!
A key issue for creating a truly efficient system is the power supply. There are more and more really efficient units on the market, and the way to recognize them is an 80plus certification. This designation means that the power supply stays above 80% power efficiency (output power vs. input power) at 20%, 50% and 100% load. In addition, there are 80plus Bronze, Silver and Gold labels, which require even better efficiency levels:
| Header Cell - Column 0 | Efficiency at 20% Load | Efficiency at 50% Load | Efficiency at 100% Load |
|---|---|---|---|
| 80plus | 80% | 80% | 80% |
| 80plus Bronze | 82% | 85% | 82% |
| 80plus Silver | 85% | 88% | 85% |
| 80plus Gold | 87% | 90% | 87% |
Most power supplies without 80plus specification fall between 65% and 75% power efficiency at their given loads. Hence, it makes sense to look for a truly efficient device. Cost is the only limit: be prepared to fork out $200 for the nicest 80plus Gold and Silver products. The 80plus Bronze devices are more affordable, but they easily reach $100 or more.
Efficiency At The Lowest Loads
Another factor to consider is efficiency outside or below the specified 20% to 100% range. If you take a 1,000 W power supply and run a power efficient system such as the ones we used for this review, they will require only 40 W when idle. This means the power supply runs at a load of only 4%. In that case, even the best-designed PSUs start to become extremely inefficient. The result may be a 40 W system requiring 50-60 W when idle, and then it doesn’t make any sense to purchase efficient components anymore.
Power Supplies Used
We used three different power supplies to emphasize the importance of efficient PSUs. The first was the one we used for testing the Core 2 Quad S-series processors, a Fortron FSP220, which is a low-power, high efficiency PSU (220 W). We added an Enermax Pro82+ (PR425AWT, 425 W), which is an 80plus Bronze device that can be considered a very good choice for upper mainstream systems. Finally, we used another Enermax power supply, the EG565P-VE, which is roughly three years old and not as efficient as the others. Check out the benchmark section called Power Supply Impact for details.
The Enermax EG565P is a rather old device. We used it to show the impact of an inefficient power supply unit on an efficient PC configuration.
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