Or you can do what we did
Just plug in an extension cord.Go to Home Depot (or your equivalent) and get a length of 10ga, three-strand wire, a weather resistant 30A male plug and 20A female and make an extension cord. Total cost was around $12. Plug it in to the shore power recepticle. We use a 4-way adapter on the end to simultaneously power our battery charger, radio and fan (or heater). It is independent of the boat's 12V system and runs only home AC appliances. No drilling holes, using expensive marine hardware, running wiring, etc. We've used this setup for 5 yrs.