I believe an Inverter from AS is an option...the dealer you bought your AS from may have added one???
You need lots of battery amp hours to run a larger inverter for very long...the smaller inverters will allow you to run your TV and DVD player for the evening if you have two batteries in your AS.
The optional AS inverter is only about 400 watts, as I recall, and is way to small (wattage wise) power your microwave...it will charge your cell phone, iPod, shaver, etc., but not the larger wattage stuff like a coffee maker, etc.
I had to install a 1500
watt inverter to be able to power our small microwave oven, and even though it 'runs', it isn't really enough power to cook stuff very quickly...it takes popcorn about twice as long to pop using the inverter, versus regular shore power.
I'm not familiar with the way AS wires the optional inverter, and where the controls are, etc...perhaps someone on the forum with that option in a new AS can help you...