Mini-Split (Ductless HVAC)

Skip the ductwork entirely and you get a mini-split: an outdoor unit holding the compressor and condenser, wired to one or more indoor air handlers mounted on a wall, ceiling, or floor inside the home. A slim conduit, about three inches wide, runs between them carrying the refrigerant line, power, and a condensate drain. The indoor unit conditions the air for its room directly, with no ducts in between.

That ductless design is the whole advantage. According to the U.S. Department of Energy, duct losses can account for more than 30 percent of a system's energy use, and the loss is worst when ducts run through an unconditioned attic. In Arizona, where attic temperatures climb well past 130 degrees in summer, ductwork up there bleeds cooling badly. A mini-split delivers its cooling straight to the room and avoids that penalty, and modern units run at high SEER efficiency.

A single outdoor unit can serve several indoor heads in a multi-zone setup, and each head has its own thermostat. That makes mini-splits a strong fit for the spots a central system handles poorly: a casita or guest house, a converted garage, a home office, a sunroom, or an addition where extending the main ducts is impractical.

For example, a detached casita on a Cave Creek property can run on a single mini-split rather than tying into the main home's HVAC, giving the guest space its own independent temperature control and its own efficient zone. The trade-off is that each indoor head is visible on the wall and serves only its area, so whole-house comfort needs a head in every conditioned space. Mini-splits should still be sized with a Manual J load calculation, not by guesswork, for the same reasons any HVAC equipment is.