Looking at a house for sale without central air, anyone know a round about cost of installing it??. . 1050 sqft ranch house, already has forced air heat (that’s all I know) and the house was built in 1955. From what I can tell… Calling a HVAC contractor will get you a much better estimate, especially if you tell them they will get the work if you buy the house. In 1980 I paid $1300 US for a compressor and coil. Another 500 for labor. A HVAC contractor can look up the cost of a 2 ton unit plus coil and add money for labor for a budget quote. This assumes you have a nice forced air furnace with room above the furnace to install a coil. When I purchased a new house a few years ago, I think they charged me 3 or 4 thousand for air conditioning. If you have a 1955 forced air gas furnace you should replace that as well. The pre 1980 furnaces have a 60% efficiency and the cheapest new furnaces have 80%.