Conclusion
We briefly discussed the components that we analyzed on the pages above, and the tables on the test results page provide a comprehensive summary of the numbers. In short, it is possible to save as little as 2 W and as much as 40 W just by a smart component choice. Sticking to mainstream DDR2 memory and average timings saves some watts, and selecting a hard drive with a low platter count also does. You can also save approximately 10 W by using a 2.5" hard drive instead of a 3.5" model.
In part one of our Power Saving Guide we also found that two high-capacity DIMMs should be preferred over configurations with four DIMMs, as the difference is approximately 8 W. Energy-saving features such as AMD's Cool'n'Quiet or Intel's Enhanced SpeedStep reduce the processor clock speed and voltage, which saves up to 50 W, depending on the processor model. Finally, turning off everything that you don't need by enabling system power saving options (standby and hibernation modes) will also have a noticeable impact.
The largest potential to save energy is hidden in the graphics card: the GeForce 8 series may be the fastest product family today, and it supports all visual features for DirectX 10, but all of this comes at the cost of tremendous energy requirements. The GeForce 8800 GTS requires 40-65 W more than a GeForce 7800 GT, which is more than the total power requirement of a notebook PC or a 20" TFT display. Hardcore gamers probably won't find a way around it, but anyone who considers efficiency a priority should consider carefully if it really makes sense to go for state-of-the-art graphics.
Should You Care?
For the average user with manageable requirements regarding performance and efficiency, we recommend paying some attention to components, as the difference between components may influence overall system power consumption by up to 40%. However, looking into all the details such as memory timings, hard drive geometry or analyzing the power requirements of add-on cards doesn't make much sense for most users.
If you care for a quiet and efficient PC for your living room or other noise-sensitive, heat-sensitive or energy-sensitive environments, you should stay away from highest-end products such as DDR2-1066 memory, the latest graphics cards and Extreme Edition processors. Go for modern hardware, but stick to integrated graphics or lower mainstream graphics if you can, and consider using a 2.5" hard drive. Also, evaluate if it makes sense to purchase low-power components such as motherboards with mobile chipsets, or a mobile processor for desktop use. We haven't evaluated power supplies, but their efficiency also has a noticeable impact.
While efficiency is important, the 10-15 W of savings compared to the 120 W power requirement of an upper mainstream desktop PC will not really have a large impact on the energy bill of one person. For corporate users and buyers, though, the issue is quite different: multiply those energy reductions by hundreds or even thousands of systems, and the potential savings can easily be thousands of dollars per year.
