Here's how the ASUS M4A78T-E motherboard stacks up in real life against a couple different motherboards. We have no way of directly measuring motherboard power draw, so PCSTATS measures total system power draw and compares that in CPU-loaded (max value recorded in Prime95) and idle states (at Windows Vista desktop).
An Extech 380803 AC Power Analyzer and A-PFC compliant PC Power and Cooling 750W power supply were used for these tests.
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System Power Draw Tests: (PCPower 750W PSU)
ASUS M4A78T-E (AMD 790GX GF 8800GTS 320MB) 
The Asus M4A78T-E motherboard has managed to tame power consumption, at idle the platform draws just 77W without a discreet videocard installed. When the videocard-less system is stressed under 3Dmark06, peak power consumption is 123W. By comparison when a Geforce 8800GTS is installed in the M4A78T-E that value balloons to 216W! In general the ASUS M4A78T-E draws less power than the DDR2-based M3A78-T system.
Let's look at the M4A78T-E's physical attributes in a little more detail.