Warning: two- and three-head units are 30% less efficient than single-head units, and units with more than three heads are 50% as efficient (based on real-life

Warning: two- and three-head units are 30% less efficient than single-head units, and units with more than three heads are 50% as efficient (based on real-life measurements, in MN IIRC). So at least pick one single-head hyper-efficient unit, like a Gree Sapphire, to heat the largest and most-used room. If you don't mind the extra condensers, one outdoor unit per head is the best