Since most mini splits are dual cool/heat, they are intended to be a backup. if I can get cool only, I will do a cost-benefit analysis to determine which way to go. One is none, two is one.
what about 48V? we get 20% efficiency off PV panels. About a 30% efficiency in the grid energy production when using natural gas or coal. if I go PV and then through an inverter, I get the PV efficiency and then 85-93% efficiency with the inverter. So which uses the provided energy more efficiently?
One thing I might add about using mini-splits. On the 4-head I installed for my brother in law, they have 2 heads upstairs in the bedrooms, and 2 heads downstairs (kitchen and living room). One thing I learned, is if I did it again, I would instead go with two smaller outdoor units, each with 2-head (a pair for upstairs, and a pair for downstairs).
Because we had gone with one single large outdoor unit of 36000 BTU, but all 4 heads (2x 9000btu, 2x 12000btu) have to share it (which is totally fine, except they can only do heating, or cooling mode whenever they want, on the fly, but not at same time)...
In certain seasons, the 2 head upstairs needs cooling, while the 2 heads downstairs may want heating, so in auto-switching mode, the ones calling for heat have to wait until the ones calling for cooling are done using it, since it can't run in both modes at same time.
Most of the time this is not a real issue (especially on a well insulated house), but say one person what to cool down a single room, but the other 3 units are heating 3 other rooms, the cooling will have to wait until the 3 heads take a break, to switch over and cool the one room.
Or the other way I might do it, is to just install 1-outdoor to 1-head unit for each room... Or do the 1-outdoor to 2-head units (for each floor), since the rooms on a floor were more likely to stay on same mode together.
My Mother's system doesn't have a problem with this since her house is insulated really well (more modern) and both floors tended to stay more constant temperature.
However it was a little more obvious at my brother in law's place because he had a 100-year old house with poor insulation so I could tell there was more tendency for it to be cooler downstairs and hotter upstairs, so the upstairs tended to want cooling more, and the downstairs tended to want heating more. So it would work on cooling upstairs for awhile, then it would switch and work on cooling downstairs for awhile, like round-robin...