If you have a seperate three rooms then you have to buy seperate three AC.
To Buy an AC first you measure a area of the room.
Area of the room determine Nominal capacity of the AC that is in terms of ton.Roughly we can say that 100 sqft room required 1 ton cooling capacity AC.
An AC cools a room by absorbing heat from room and throwing outside, this is known as cooling capacity and it is measured in Btu/hr.Btu means British Thermal Units per hour.
12000 Btu = 1 Ton
Cooling capacity depends upon size of the room,outside temperature,how many people are in the room.
You can get calculator from website to know how many ton AC you can buy.
Today people prefer spilt AC because it gives more cooling for large area.If your room size is more and you want less noise then go for spilt AC. As the spilt AC has two unit one unit inside and another outside, because of this two units spilt AC makes less noise than window AC.If your room has window for AC then only you can think for a window AC.
For new home interior wise spilt AC's are good because spilt AC require a small hole in the wall and it goes beyound the AC.But spilt AC are expensive than window AC.
While choosing a AC first you check the following features:-
1. Energy efficient setting.
2. Easy maintenance - filter should be easily removed and cleaned.
3. AC should have dehumidifier that reduces a humidity makes it cooler and comfortable.
4. Noise level it range from 30-60 decibel.
5. Star rating given by BEE- most of the AC's given a stars which detect the energy efficiency.
6. Sleep mode of an AC which automatically adjust temperature during night.
7. Auto restart facility-whenever power goes AC stars automatically in same mode.
8. Air flow direction.
9. Cooling capacity.
10. Compressor Type
Rotary - compact and less noisy.
Scroll - quitest and most efficint.
O general is a good AC it support all the features given above but in India we get a India manufacture unit so go for either LG or HITACHI.
LG support two new features -
1 Chaos Logic - air flows in different angles
2 Fuzzy Logic - saves energy
Specification LG 1.5 LG 1.5 Hitachi
Model LSASEW5V LSASMQ3M RAU318HID
Compressor type Rotary Rotary Rotary
Nominal capacity 1.5 1.5 1.5
Cooling capacity 5200 5225 5363
star rating 5 3 3
noise level 30 36 34
Auto restart Y Y Y
Sleep mode Y Y Y
Air direction Y Y Y
Anti bacteria Y Y Y
wt(indoor unit) 16kg 13kg 12.9
wt(outdoor unit) 37kg 39kg 43
Price 38,490 31,900 36,500