Considering portable a/c vs our old Central Air, from 1992, in 2 story, 2300 square foot house, High Desert
I can't provide product specs, but can share that when my central AC died last summer in a heat wave I bought a couple of very small (I could lift and install by myself) window units.  $tressed about fixing central - until my electric bill came in at a fraction. 
Similar, only need to cool a couple rooms to be comfortable