BTU stands for British Thermal Unit. 12,000 BTUs = 1 ton of refrigeration, 18000 BTU = 1.5 ton and so on. Its not like higher the better, it all depends on the volume of your room and that should dictate what tonnage you require. Normally, good brands do have sort of calculators available on their websites. I have ordered 16,000 Btu unit from , will be delivered in a few days. Will share the data sheet on the forum for information of all.