How BTU is Related With The Area Of Room?

The price of a room air conditioner depends upon the BTU quantity.Generally small room needs low BTU capacity and large room needs higher BTU capacity.For example a small room (150 to 300 square feet),select an air conditioner of 5000 to 8000 BTU/hour.For a large room (600 to 1000 square feet) 10,000 to 15,000 BTU/hour is suitable.In the above consumption the height of the room is considered as a standard measure.If the room is not completely insulated,the height of the ceiling is very high and it is situated at south faces window,the BTU capacity of the air conditioner will be extended up to 10% probably.It should be clear to everyone that if we use lower BTU capacity in a large room,the air conditioner will turn off and on around a long time decreasing the efficiency.Again if we use air conditioner in a south facing window room,the air conditioner take more time to cool down the room.So in this case larger BTU capacity containing air conditioner should be used for lowering the electric cost.