9.5 years later:
10-year warranty Duratherm geyser started leaking, no warranty, they changed it.
Replacement tubes were nowhere to be found, as a few had no more vacuums.
Pump needed replacement.
Eskom damaged the Geyserwise system, which triggered the in-depth investigation.
±R25k to replace it all.
Bugger no!
Solution:
4 more panels
2 x 2kw elements
2 x Geyser Wise timers, the cheap ones.
1 x B+ Rated geyser.
… and use the existing grid-tied inverter to warm the geysers, on schedules, as the 2kw elements fit nicely into the exiting house loads during the day otherwise I will have had too much paneling, even before the 4 more, if not for the geysers.