An investigation was carried out in a multi-family building in New Jersey, USA of eight apartments, including resident interviews about air conditioner usage. Energy consumption for cooling varied widely across similar apartments, due to occupants' diverse beliefs about machine operation and economic considerations. 75% of residents did not use the thermostats, preferring to switch the system on and off according to comfort needs. Concludes that the problem is not lack of user education, but rather poor user-friendliness of air conditioner controls. The overall result of the on-off operation was to save energy, even though conditioners were set to maximum. Suggests modifying air conditioner controls to accommodate this type of operational behaviour.