Depends on whether the sun shines and how many other people are hogging the hot water! Seriously, I think that you will find that most solar water heating systems can be electrically boosted and the owner will switch this on if there is insufficient sun to bring the water to a reasonable temperature. Last September at Anna's we found the water tepid in late evening. early morning until Anna showed us where the electrical water heating switch was located and we subsequently made sure that we didn't suffer cold showers again!
Best wishes
Allan
