Well, our old water heater decided to pack up, so that was a sign to go ahead with a solar water heater, which was installed a couple of weeks ago. Had a choice of evacuated tubes or a flat panel, and it wasn't that clear-cut. Apparently the evacuated tubes are more efficient than we need in the South African summer, and they can over-heat the water to the extent that water is wasted as the pressure valve releases water. In winter the tubes make sense, but the consensus seemed to be that overall, over the course of the year, flat panels are best for this climate.
Eskom seems to agree with that assessment, as the rebate is higher for the flat panel system. But they are gradually reducing the rebate, apparently with the intention of phasing it out. No idea why.
Next thing will be to find a use for the old water tank, which we left in the attic so it could be used for a gravity-fed recycled water system.