After electricity was discovered, the question was raised: Does one fulfill the mitzva of lighting Ĥanuka candles with electric bulbs? In practice, most poskim maintain that one may not use electric bulbs, because they are not considered “candles,” which have wicks and are fueled by oil or wax. Furthermore, since they emit a very strong light, they may be considered “torches” (avukot), which have multiple flames, not candles (“nerot”) which have a single flame. R. Avraham Yitzĥak Kook writes that since electricity did not exist when the Sages instituted the mitzva, it is not one of the types of candles included in the rabbinic enactment that one can use to fulfill the mitzva (Mitzvat Re’iyah, oĥ 673).
It is true that regarding Shabbat candles, most authorities maintain that in a time of need one can fulfill the mitzva, with a berakha, using electric lights, because the main purpose of Shabbat candles is to provide light. Ĥanuka candles, however, are meant to remind us of the miracle. Therefore, they must resemble the candles used in the Holy Temple, and since electric lights are not similar to candles, one does not fulfill his obligation by lighting them.
Be-di’avad, if one does not have an acceptable candle, he may light electric bulbs, without reciting a berakha. By doing so, he affirms the miracle and, according to a few poskim, even fulfills the mitzva.
Some have a custom to place large, electric menoras, whose light can be seen from afar, in public areas. Even though this does not fulfill the rabbinic commandment to light Ĥanuka candles, there is merit to this custom, because it reminds the public of the miracle of Ĥanuka.