So many different views and experiences!
To add my bit : we have 2 Mitsubishi Electric units in adjacent bedrooms, one a Mr Slim, one not. Both are some 10 years old. The Slim cools the room very efficiently, sometimes too cold for me; but has needed 2 replacement temperature sensors. The other just will not cool the room adequately now (it did so originally). Both are cleaned about twice a year by contractors.
Asked why the two do not cool similarly the contractor engineer replied that the Slim unit is a bigger one that the other - but in fact they are both 24500 BTU rated.
So I am less than satisfied with Mitsubishi Electric, and I am looking to replace one unit, so your comments are helpful even though very varied.
A local shop offered me Daikin models at 20500 or 25500 BTU rating, but wanted me to choose. Online sites that calculate size for my room give values from 9000 to something over 30,000 BTU !
So please can anybody assist me, or point me to a reliable source, to determine the appropriate size for a new unit ?
Tom.