We measured power consumption using Extech Power Analyzer 380803 device. This device was connected before the system PSU, i.e. it measured the power consumption of the entire system without the monitor, including the power losses that occur in the PSU itself. When we took the power readings in idle mode, the system was completely idle: there were even no requests sent to the hard drive at that time. We used LinX program to load the Intel Core i3-540 CPU. For more illustrative picture we created graphs showing the power consumption growth depending on the increase in CPU utilization as the number of active computational threads in LinX changed in nominal mode as well as during overclocking. The boards are sorted out in alphabetical order on the diagrams below.
The power consumption of the full-size ASUS P7H57D-V EVO is far higher than that of most other mainboards, but we can put up with it because this LGA1156 mainboard is a unique product with ultimate functionality. ASUS P7H55D-M EVO and EVGA H55 are not economical when idle irrespective of whether they are overclocked or not, although the power draw of the EVGA mainboard is lower than that of most other mainboards during overclocking since it overclocks to a lower level. The power efficiency of the rest of the mainboards is similar. We can only note that Intel DH55TC and MSI H57M-ED65 are more economical than the others in nominal mode.
As for Zotac H55-ITX WiFi, it is highly economical when idle or under low load, but this changes as soon as the CPU is fully loaded. The power draw is lower than with most other mainboards during overclocking because the frequencies and CPU voltage are lower than those of the others, too. It is comparable to the power consumption of EVGA H55 but the latter is a full-size mainboard and besides, it is very power-hungry anyway.
What I don’t like at all is that Zotac consumes a lot of power under full CPU load when working in its nominal mode. It needs more power than any other previously tested mainboard, reaching as high as 130 watts. This is all due to exceedingly high CPU voltage. Power efficiency is one of the priorities for compact mainboards as it helps reduce heat dissipation and noise, so this is indeed a serious problem.