If a Yid is on boat during Shabbat and he can’t use fire for Shabbat candles or for havdalah, bedieved does he have an option?
The general consensus of halachic authorities is to consider electric incandescent light bulbs as actual fire, and therefore permit the use of light bulbs for purposes of Shabbos candles, even with a berachah (Shemiras Shabbos Kehilchaaa 43, note 22; the status of a light bulb as halachic fire has already been ruled by the Achiezer, the Beis Yitzchak, the Chelkas Yaakov, the Tzitz Eliezer, and others).
The reason for this is that enactment of lighting candles was made for the purpose of having light in the house: For oneg shabbos (for the enjoyment of Shabbos, ensuring that people will not stumble in the dark) and for kavod shabbos (in honor of the Shabbos).
Although electric lighting should not be relied on under normal circumstances, it is therefore permitted under extenuating circumstances.
However, the Or Le-Zion (Vol. 3, p. 189) writes that one does not fulfill the obligation of Shabbos candles with electric lights, because the “fuel” for the light is not present at the time of lighting. When a person lights a candle, all the wax or oil needed to sustain the flame is already present. An electric lamp, however, is sustained by the electric current that is constantly being fed into the lamp. Since that current is not present at the time of lighting, one cannot use such a light for this obligation.
Based on this and other reservations, some rule that a berachah should not be recited when electric lights are used for Shabbos candles (see Shraga Ha-Meir 5:11). As noted, the majority opinion is that a berachah can be made upon turning on the lights in honor of Shabbos.
The issues are essentially the same with regards to Havdala, and many authorities rule that one may use an electric light in place of a Havdalah candle in a time of need (see She’arim Metzuyanim Be-Halachah 96:6; Az Nidberu 8:2; Rivevos Ephraim 3:599).
In fact, it is reported that Rabbi Chaim Ozer Grodzinsky would always use an electric bulb for Havdalah, in order to demonstrate how strongly he felt that electricity is to be treated exactly like fire from the perspective of halachah.
However, some object to the use of electric light bulbs for havdalah purposes, because of the glass casing that covers the fire.
Note also that for purposes of havdalah, only an incandescent light bulb, which has the full status of “fire,” can be used. For Shabbos candles, many authorities write that even fluorescent sources can be used.