My 12v socket in my Scania is rated @120W, yet my inverter is a 600w item!
A little worried about this, I asked my dealer if this was a problem and was told as long as I did not run a Microwave oven or similar from it, it would be absolutely fine!
The main point he underlined to me was that to not leave it on constantly, the socket is switched & it goes off when I switch off the ignition, I never goto bed in the truck leaving the ignition on......
Despite the above, I know of a driver with a Scania similar to mine, he has a Microwave, TV/DVD, Laptop & kettle plugged into a 4into1 adapter into his 1500W inverter, yes, running from the 120W 12V socket! - I also know of a guy with a desktop PC setup in his cab(!) - neither have not gone up in flames - yet!!!
I now have an adaptor in it, so my laptop & 'phone charger can be used at the same time.