An air conditioning unit in Watertown typically costs between $102 to $878 to be installed. That is for centralized air conditioning units. For a much smaller window air conditioning unit, the price is about $300. Air conditioning brands and types can add up to the general cost of acquiring an AC. The price range for a brand air conditioning unit is from $1400 for Payne units up to $3400 for a Lennox brand. Other available brands of air conditioners are Aire-Flo and Coleman which cost around $1700, Frigidaire for $2900, American Standard and Carrier that are both priced at around $3200, and Trane for approximately $3300.