What size condenser do you need for central air?

It depends on a number of factors including location, layout and size of house, number of Windows, type of Windows, insulation, etc. Usually you would want a contractor to come out and do a manual j (heat loss and gain report) to make sure that you get the right size unit. Too big and it will cycle on and then shut off and may make the air drier than normal in your house. Too small and it will be constantly running on hot days trying to cool the house. There is some software you can download for $50 to do the report youself ( http://www.acdirect.com/new_faq/faqs.php?gclid=CKSi2qTw7ZMCFQE4GgodRxHeVg) or you can use 1Ton per every 500sq ft of conditioned space as an estimate. Hope this helps