People often get confused over BTU's or the Tons of a unit. 


It's simple : 


  9,000 BTU  =  3/4 TONS

12,000 BTU  =    1  TON

18,000 BTU  =  1.5 TONS

24,000 BTU  =    2  TONS

30,000 BTU  =  2.5 TONS

36,000 BTU  =    3  TONS