With regards to mini split A/C units, it would appear efficiency comes at a cost.
Case in point, I have two 9000 BTU inverter splits, a Diakin with a linear compressor, R32 refrigerant, SEER 28, installed cost ~$750.
The other a Samsung rotary compressor, R 410A seer 18, installed cost ~$425
The power consumption rating for the Diakin is 510W, the Samsung 840W, these are averages, both are capable of both higher and lower depending on demand. This is where the Diakin clearly outperforms the Samsung, the linear compressor is capable of lowering power to 150W in temperature maintenance mode, the lowest seen for the Samsung is 425W.
The Diakin is used at night, Samsung by day as required, the temperature setpoint I use is 28°C, although it may seem high, though lower than outside, the most important factor is, it reduces humidity, which takes the edge off allowing a more comfortable sleep. Being offgrid one still needs to consider the limitations of the battery, hense the conservative use.
Note. The prices stated are in Thailand but demonstrate, to me at least, that it's better to spend a little more up front because batteries will ultimately cost more than the differential between the initial cost of the units themselves. Don't go broke saving money is my motto.