My children had a power outage this erev shabbos that lasted until 11:30 pm. The Cholent was fully cooked before power went out.
1. Can water in urn be used?
2. Can the (now reheated) Cholent be eaten the next morning?
3. If daver lach is a consideration in the above, is a tavshil like Cholent that invariably has some liquid in it considered a daver lach?
There is some room to be lenient, even for the water, and greater room for leniency concerning the cholent, if it has a solid texture.
Certainly, if the food is required for the Shabbos meal, there is room for leniency.
The cholent will not be considered a “davar lach” (liquid) if it is principly solid (most cholents are), even if it has a slight amount of liquid. Only if there is substantial liquid is a food/dish considered a davar lach.
In general, questions of electricity depend to a degree on whether the location is Israel, where Jews do the work, and the US, where it can be assumed that non-Jews do the work to fix the electricity.
However, in the case of a power outage, because of the many electrical machines that are vital for sick and elderly individuals and are required to keep them alive, it follows that even if the electricity was fixed by Jews, it remains permitted to derive benefit from it.
Yet, the above addresses the question of using the electricity per se. In our case, there is an additional question of chazarah: The pot or the water were “off the fire” on account of the power failure, and we learn in siman 253 (Rema 11; Be’er Heitev 11) that if a non-Jew puts a pot that has entirely cooled back on the fire it is forbidden to derive benefit from the non-Jew’s heating on Shabbos.
[This assumes that the conditions of chazarah are fulfilled in cases of a power failure — meaning, that if the liquid will not have cooled, there would not be a problem. See Iggros Moshe, Orach Chaim 4:74, bishul 38; Shemiras Shabbos Kehilchasah Chap. 1, note 69; but see Chazon Ish 38:2 and 37:21, disputing the Mishnah Berurah 253:33-34, according to whom there is no room for leniency, and see Orchos Shabbos, Chazarah 49-50.]
Yet, there is room to compare the case of a power failure to setting a timer to turn on the fire during Shabbos — meaning that the heat goes on “automatically,” rather than by means of a melachah. The reason for this is that the non-Jew is not actually “turning on the fire,” but only fixing the electricity, and the fire goes on automatically as a result.
For a fire that goes on authomatically, the Tzitz Eliezer (7:16) rules that one can be lenient (this will not be true according to the Chazon Ish noted above), and see also Me’orei Ha-Eish p. 81, citing from Rav Shlomo Zalman Auerbach (concerning a covered flame). However, several poskim are stringent, as cited in Yalkut Yosef (Vol. 3, p. 232).
See also, at length, Otzros Shabbos (Koritz), pp. 205-207.
For the purpose of a mitzvah, such as for the Shabbos meal, one can rely on the lenient opinions.
If the cholent is solid, there is greater room for leniency, because the problems of chazarah noted above apply specifically to liquids, for wihch there is a possible Torah prohibition in re-heating.