Window Air Conditioners with inverter technology are a game changer.  They are energy efficient, quiet, light weight.  The 10,000 BTU I installed when my whole house heat pump died keep me going through a stretch of 100+ degree days and did a great job.  My house is insulated with foam in the walls and on the roof, so it's has a great thermal envelope, and the unit kept the whole 950-SF below 78-degrees F.