Take note though of other threads on how much
laptops draw.I've had quite a bit of experience with that over the last 7 years.
It seems to vary between 3 and 5 amps at 12 volts DC depending on the
laptop and inverter combination.

Well my the power supply on my sony Vaio pcg-k37 (the laptop I use to
render video) says it needs 20 12 volt amps input. It really does use
about that much when it's working hard. I keep another laptop for
charting and it uses about 3 12 volt amps.

-- Tom.