What size central air conditioning systemis recommended for 1200 square feet? A 1200 square foot home needs a 23,000 BTU central air conditioning system. It is very important to choose the correct capacity air conditioning system for a home. How can you estimate the cost of installing central air conditioning? What is an air conditioning condenser? Air conditioners are designed to remove both heat and humidity from the air. Many people buy an air conditioner that is much too large, thinking it will cool their house faster and therefore use less energy; however, this is not the case. An air conditioner that is too large will use more energy, and although it may cool the room more quickly, it will not remove all of the humidity in the room. If the proper size air conditioner is selected for a home, the energy bill will be lower and a house will be more comfortable. Where are the costs associated with installing a home air conditioning system? As of February 2015, the average cost of installing a home air conditioning system is between $4,000 and $6,000.