Both window AC’s and portable AC’s are really designed for cooling single rooms. A window AC though, under certain conditions can serve to cool even a few rooms where there’s good airflow. And it can cool large rooms no problem. A portable AC is less likely to be able to cool as much space. And a window AC generally will cool a space more quickly.

Also there are many window AC’s which are Energy Star rated. Portable AC’s though do not have Energy Star Ratings. There are no current regulations established with portables being more of a newer technology. It does not mean that there are not energy efficient portable AC’s, it’s just more difficult to know which one’s are most efficient when shopping for them.

Still, portable AC’s are rapidly improving and there are already many available with a proven record based on hundreds of reviews. Many satisfied customers report that their portable AC does very well cooling even large rooms and quickly enough at a decent cost for electricity. It will all depend on the room conditions and getting a model with the right amount of BTU’s for your sized space.