Is a 9,000 BTU split unit too big for a 144 SF room. It seems that these type units can't be found any smaller than 9,000 BTU
Generally a 7,500 to 14,000 BYU is ideal for a room that is 800 square feet. This is especially in a case where the air conditioner is portable. You need 6,000 to 7,500 BTUs for your room. Visit http://www.ehow.com/info_8094276_btu-air-conditioner-do-need.html for more information.