Many portable air conditioners have two air tubes outside: one for the intake and output of hot air, the other for fresh air. Some portable air conditioners go one step further and include a "dry mode" that slows down the fan, allowing the condensed vapor to sit longer and further dry out the air. To ensure that the unit works properly, make sure to clean and vent it properly. The first step in maintaining any ductless air conditioner is the cleaning and changing of air filters. In comparison to wall-mounted split-system units, portable air conditioners require more power to accomplish the same task. Some stand alone units are battery powered, making them easier to move into another room. Portable ACs do not require installation, unlike central ACs or window ACs. It is important to maintain battery-powered ACs. Portable units also have the motor inside a small room. The fact that these units take valuable floor space is what many people dislike most. Installed into the ceiling, ducted central air conditioners are similar. Portable ACs based on refrigerant have the same technology used by traditional window ACs. As prices of electricity increase, the use of electrical appliances is expected to decrease.