If a unit is too big for the room, it will cause the unit to short cycle, which means the output of the unit will ramp up and down too frequently. This can lead to fluctuations in room temperature and excessive noise. As a helpful guide to finding what size heat pump / air conditioner you may need, you can use the Fujitsu Assist Tool, located on our website. However, the best way to find out what size heat pump / air conditioner you need for your room or home is to contact one of our Fujitsu Accredited Installers who are able to assess your space and determine the best unit to suit your needs.