Dual Power Outlet

First, it depends on the collective current draw of the laptop and the GPS. At worst though, you would probably just blow a fuse.

Second, do you know you have a second outlet in the middle storage area between the two seats? Thus, you should have two outlets right up there by you.

 

We don't have enough info. How much power does your laptop typically draw thru the plug? That can vary a HELL of a lot. You can measure that via a device like http://www.p3international.com/products/sp...0/P4400-CE.html.

What is its max? To find out the max, I'd max out the CPU at 100% (client from www.distributed.net is good for that), run a graphics benchmark (http://www.futuremark.com should suffice), run the optical drive (maybe just copy a CD or DVD to the hard drive) AND totally drain you laptop batteries (or batteries) so that laptop is forced to charge it. I vaguely recall my ancient Dell laptop (Inspiron 4000 800 mhz Celeron) pulling at least 70 watts thru the plug when CPU was maxed and it was busy charging dead batteries.

You then need to factor in how many amps an inverter might draw above and beyond the # of amps the laptop pulls (not sure of their typical efficiency) and figure out whether that will go over whatever the fuse rating is on fuse tied to the Prius' power outlets. I doubt that GPS unit will draw very much.

To be on the safer side, you might want to remove the laptop batteries while running off an inverter to prevent any extra draw from charging.

 

If you can get enough power for two devices, just use an adapter to convert to 2 outlets. But get the kind on cords.
I tried the one to 2 adapters that are all in one and they shake loose in the outlet very quickly.