That problem was solved 20+ years ago. Typically you have an element halfway up the tank, so the electric heats the top half only, but the solar heats the full tank.
Ripple, timer, or remote control can shift electrical consumption to times of lower cost (overnight, mid-afternoon) while having negligible impact on quality. A big tank will stay hot for a few days easily.
That problem was solved 20+ years ago. Typically you have an element halfway up the tank, so the electric heats the top half only, but the solar heats the full tank.
Ripple, timer, or remote control can shift electrical consumption to times of lower cost (overnight, mid-afternoon) while having negligible impact on quality. A big tank will stay hot for a few days easily.