1. We learned yesterday that the prohibition of bishul does not apply to cooking directly in the sun, which is permitted since it is not a normal method of cooking. Poskim disagree as to whether solar heating systems (found mainly in Israel, known as dud shemesh) are included in the prohibition of bishul or not. On one hand, the water is heated from the sun, but on the other, it may not qualify as direct heating since the system is more complex than simply having water heated directly from the sun, and we learned yesterday that only direct heating in the sun is permitted. In addition, some are concerned that one may come to heat up water using the electric heater rather than the solar heater or that certain solar systems in large buildings involve heating the water via other hot water rather than the sun.

2. Although the issue is complex and beyond the scope of this forum, the bottom line is that it is usually recommended not to turn on hot water from the tap even where a solar heater is in place. Even though the water in a dud shemesh may have been heated by the sun, opening a hot-water tap can create a number of halachic concerns and is therefore generally avoided. However, there is room for leniency in certain cases, which one should discuss with a halachic authority (see Shemirat Shabbat K’hilchatah 1:51; Peninei Halacha, Shabbat 10:25).

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Dedicated by Fran Broder as a zechus for everlasting peace in Eretz Yisrael in the merit of learning Hilchos Shabbos.