Thanks GottiBoi55. I'm hoping to find a cheaper third-party adapter instead.

well it depends.

for Office use, and light use, it will do super fine and charge the battery at the same time.

just don't use it for intensive GPU + CPU 🙂

90W
Office use, browsing, battery charging at the same time.

120W
works fine for CPU 3DS Max Renderings or AutoCAD work.

180W for the intended use for G75VW/X series 😉
CPU + GPU stuff like gaming.

the GPU itself uses 75W at full load
GPU is rated for 45W with Turboboost to 50W something.
and calculate in RAM/Screen/Motherboard etc 60-70 watts ish
personally use those chargers. just know that the ASUS 120W adapters tend to die/fail...