Dry mode is cheaper than cool mode on your AC but dry mode does not cool the room.
Dry mode only removes humidity from the room and does not cool the room so if you want a cool room when it's hot out you must use cool mode.
AC dry mode is basically a setting that allows the air conditioner to operate as a dehumidifier to pull moisture and humidity out of the air.
Dry mode on AC is meant to be used when conditions are humid but the temperature is not hot.
When the AC is on dry mode it will only dehumidify and not cool the room.
If you just need humidity removed from the room then using AC dry mode can help and save you money.
However if it's hot out you want the AC to be on cooling to remove both humidity and cool the room.
Essentially, the purpose of the “dry” function mode is to reduce the excess humidity or moisture in the air, and the cooling effect comes from the removal of that excess moisture.
It works similarly to the cooling mode, but detects temperature differently.
Dry mode is intended to be used when the conditions are humid and temperatures are not hot.
It's for those days where the weather has a tropical feel and just a little too cool to use cooling mode.
An example of this would be those days when it's been raining, or about to rain and the humidity is high.
Dry mode will not remove 100% of the moisture in the air.
Instead, it will help lower the humidity to a healthy level.
However, it's recommended not to run your AC on dry mode for more than 1-2 hours at a time to avoid drying the air too much.
Thanks to the low fan speed and shorter duration of compressor operation, the AC dry mode also saves electricity significantly unlike a full-powered dehumidifier which completely dehumidifies a room but consumes a lot of power in return.
Using air conditioners on dry mode, hence, can save you up to 30-50% of energy.
The dry mode on AC is only effective in cooler weather so don't try to use it when it's a boiling hot summer's day. On those days, you should rather opt for the cooling mode setting on your air conditioner.
If you are looking at switching to dry mode in your car, it is ideal for when you want to defog your windscreens internally.