Well, if she "put the multi meter leads on the end of the positive and negative wire coming in off the solar array", she was obviously measuring voltage. So it could be 17.4. Not particularly relevant.
A few points I would like to make. Personal opinions, obviously.
- Panels, they sell them everywhere. Why have them shipped from far away? Just buy locally.
- Technical specifications are all good and fine. Real life is more... real :·)
Four 300W panels (well, 2 if they are 12V and you need 24) plus (I guess) some 400 Ah of batteries, should be fine to run a 1000W A/C unit.
If you run it during the sun hours, and use the generator on overcast ones.
Even though, 300W, it's theoretical. Real-life, call it 150. Non-ideal angle, non-perfect radiation, heat...
Likewise, and in this case I see this as the crux of the matter, a 3KW inverter. To run 1KW.
Sporadically, fine. Continuously, for four hours... it won't like it, and above all you won't like it.
It will get extremely hot. The fan will be on all the time at maximum power. It will suffer and degrade.
It seems to me... as I've said, they do sell 24V evaporative coolers. Not expensive.
That would take the inverter out of the equation and basically solve the problem.
[EDIT] Actually, looking at the evaporative coolers... they seem to be all small and inefficient.
I can find quite a lot of full "split-unit" DC air conditioners, though.