I'm looking into more efficient water heating for the Cape Town area.

There are a few things putting me off solar water heating, namely the months of May, June, July and August. Cloudy skies mean that the solar radiation reaching the ground is much reduced. The figures for Pretoria / Johannesburg are about 50% higher for these months.

This is making me lean towards heat pumps instead of solar water heaters.

Does anyone have any experience with this in the Cape Town or PE areas (which have very similar solar radiation figures) that they'd care to share?