I am in need of a power adapter for the car that will allow me to power various electrical devices - just one at a time. I guess the most demanding thing I will be powering will be my laptop. I want to go with a DC-AC converter. It seems it will provide the most flexibility for me. Anyway, it seems that the most popluar options are 90-120-140 watts. I know nothing about this and wanted to know if my laptop can work on the 90 watts version? If so, why would you want 140 watts? Thanks for any help. I actually looked on the power line for my laptop and it has no wattage requirements listed.