We performed our power consumption measurements using an Extech Power Analyzer 380803. This device is connected before the PSU and measures the power draw of the entire system (without the monitor), including the power loss that occurs in the PSU itself. In the idle mode we start the system up and wait until it stops accessing the hard disk. Then we use LinX to load the CPU. For a more illustrative picture there are graphs that show how the computer power consumption grows up depending on the number of active execution threads in LinX (both at the default and overclocked system settings).
Because of compatibility issues we uncovered with Gigabyte GA-Z77X-UP4 TH and Gigabyte GA-Z77X-UP5 TH mainboards with our original CoolerMaster RealPower M850 power supply unit, we had to replace it with Enermax NAXN ENM850EW. Both these PSUs have very similar technical characteristics, but Enermax NAXN ENM850EWT is about 1-3 W more energy-efficient than the Cooler Master unit. In order to be able to use the previously obtained results, we decided to make up for this efficiency difference by adding 2 W to all new power readings, so that we could still compare their results against the power consumption of all previously tested products.
There was a time when we used to repeat that Asus mainboards weren’t particularly energy-efficient and consumed more power than others. It is indeed so, when we are talking about flagship models with extended functionality and numerous onboard controllers. However, the charts show that there are in fact quite a few mainboards from other manufacturers, which consume more than Asus boards. But once we take a board like Asus P8Z77-V LX, it immediately falls into the energy-efficient category. Moreover, its power consumption may be further reduced by enabling all power-saving options in the BIOS, including the proprietary “EPU Power Saving Mode”.
The situation doesn’t change during overclocking and Asus P8Z77-V LX remains among the most energy-efficient boards. Of course, we should keep in mind that quite a few boards overclocked the processor better and that is why they consume more power. However, Asus P8Z77-V LX looks great even among those boards that achieved the same overclocking results.