and finally my conclusion…
This architect’s conclusion for conditions in South Africa is that a combination of systems seems to be the most sustainable option.
My personal preference, layout and budget permissible, is for a high pressure, evacuated tube, solar system with vertical tanks connected in series to feeds bathrooms, with additional water heating sources to other area’s in order not to tap the hot water store.
Rather than use one large storage tank two smaller tanks mean the entire water store is not diluted when one tank is empty. As is the case in most households, kids tend to bath in the evenings and parents in the morning. Two tanks allow for enough solar water for both.
My preference is to use a gas geyser to the kitchen, where small amounts of water are required intermittently with a small electric geyser on a timer in a guest suite that would only be turned on when required.
Each application is unique so may differ, and needs to be examined according to the budget, hot water requirements and layout. I do hope my two cents (opinion) has helped you start thinking about your hot water production.