Determine the necessary BTUs based on the size of your home. Typically, we follow a 20 BTU per square foot guideline. Example: You would require 1,500 x 20 = 30,000 BTU output for a 1,500 square foot residence. Use one micro split with 30,000 BTUs, two with 15,000 BTUs, or three with 10,000 BTUs.