But if you're installing one of the best portable air conditioners in 2026, placement matters. You should leave at least 20 inches of space between the unit and the wall to help ensure the system can operate properly. This allows the AC unit to take in and release air from the room without any obstruction blocking the flow, leading to better performance. In contrast, airflow can become restricted when a portable AC is pushed too close to a wall, furniture, or other objects. Having enough space around a portable AC unit is also important because of the exhaust hose that connects the unit to a window kit.