The custom is to light Chanukah candles in the synagogue with the recitation of all the Berachot for the purpose of Pirsumei Nisa publicizing the miracle of Chanukah. The candles in the synagogue are lit in between Mincha and Arbit, even though the proper time for lighting has not yet arrived, because if we wait until after Arbit the congregation will disperse, thus undermining the desired effect of Pirsumei Nisa.
As mentioned, the one who lights the Chanukah candles in the synagogue recites all the Berachot, including the Beracha of Shehechiynau on the first night.
One does not fulfill his personal obligation of lighting Chanukah candles with the lighting in the synagogue. Even if one is present at the synagogue lighting, listens to the Berachot and answers, "Amen," he must still light when he returns home. Moreover, even the person who lights the candles in the synagogue must light again at home with the Berachot. The only exception is that on the first night of Chanukah, the one who lights in the synagogue does not repeat the Beracha of Shehechiynau at home if he lights only for himself. If he lights for his family, then he must repeat even this Beracha. For this reason, it has become customary to choose somebody who will not be lighting for his family, such as a single person or a traveler away from home, to light the Chanukah candles in the synagogue. According to some authorities, even a Katan (child under the age of thirteen) who has reached the age of Chinuch (training in Mitzvot), such as an eleven or twelve-year old child, may be invited to conduct the synagogue candle lighting on Chanukah.
The candles in the synagogue are lit only if a minimum of ten people are present. Both women and men count towards this minimum quorum. If as occasionally happens on Erev Shabbat ten people are not yet present but this number will undoubtedly be reached a bit later in the service, the candles may be lit, but without the Berachot. Therefore, whenever possible, the people present should wait for ten people to arrive before conducting the synagogue candle lighting.
