I'm in the high desert of Southern California. We're in a 2300 sq foot home, 2 stories with 3 bedrooms and 1 master bedroom on second story. The house is cooled by 2 central air systems, manufactured in 1990. The second story is cooled a Rheem Classic X Rahe-030jas, with the tag in the picture below. Supposedly its 208/230 Volts, 18 Amp single phase. Google says its SEER rating is 10. I'm thinking of putting Honeywell a portable mn10cesww, 10000 BTU (ASHRAE-128 Standard) / 5500 BTU (DOE+ 2017 Standard), in the master bedroom, and two bedrooms, and not running the central air at all this summer. I care only about cooling those 3 rooms. Plus I already have a small window unit in the a 4th bedroom/office, that's rarely used. The central a/c also cools the hallway and bathroom on the second story.
Will running the portables in each room at night be more efficient than running the older central air at night, especially considering that they won't be running when nobody is in the room?