Neither. It will draw what your computer draws from it, plus inefficiency. I hear that average inefficiency for inverters is 20%, but I don't really know. To calculate that, you would do [computerspower] x .20 + [computerspower] = [power drawn by inverter]
Your 145 watt psu doesn't draw 145 watts either. It draws just what it needs to run the computer, and once again, plus inefficiency. With a 145 watt psu, I would GUESS that your computer may draw around 80 watts or so. That is only a guess.
If you really want to know what your inverter draws, get an ammeter and connect it in series with one of the 12v power wires and power on your computer.