I'm not sure using a Prius (or other hybrid auto) as described is a very efficient option and certainly is not a reason in itself to buy a hybrid car/truck. Use of a Prius may be expedient, but it isn't a good use of such a spendy asset.

A standard genset such as one of the Honda Generators and a storage device such as a Xantrex Powerpack and you can have a portable system that is quiet and fairly efficient wrt use of gasoline. Use the generator to power your refrigerator and charge the battery, and then shut down the generator and run the fridge (or whatever) off the battery.