Tbh I wouldn't recommend air con
A more cost efficient and viable 12 month solution would be mvhr with a built in comfort cooler.
For those who don't know the mvhr removes moist warm air from the rooms in the winter and replaces ot with fresh air from outside. It also has a built in heater to warm the air.
If you have a comfort cooler Inc, this takes fresh air from outside and chills it before distribution to the room.
They are a lot more efficient than AC and are self serviceable every 12 month with simple filter changes