honestly guys the blanket statements given just dont make a lot of sense.

1. inverter only saves at specific temp range.

false: inverter saves WHENEVER its not used under full load. This is a huge difference.

2. appropriately sized: true inverter or not aircon must always be appropriately sized. otherwise it wont do any good. appropriate depends on your very specific cool requirement and the level of insulation and airexchange in your room. for a badly insulated room you might need 2 HP while for the same room and temp setting you only need 1 HP with good insulation.

3. Minimum hour of usage to save

There is no minimum usage to save. You save from the first minute onwards (under non full load conditions). It's a question of breaking even.

Since inverters are deemed to run with less stress on mechanics they should also last longer - how much i dont know. Guess is around 30-50% longer lifespan. since the inverter costs you around 30-40% more vs. the same model non-inverter you already break even on the lifespan savings. any additional savings will be from using less power.

so wether you use 24/7 or just 3hrs per day - you still save power.