Question: We are going to eat the Shabbat night meal at my parents’ house and we are then returning home to sleep. What is the earliest time we can light Shabbat candles at home?
Answer: One may not light Shabbat candles too much before the onset of Shabbat. Rather, one should light Shabbat candles close to the onset of Shabbat, approximately a half-hour or forty minutes before sunset, so that it is recognizable that these candles are being lit in honor of Shabbat and not for some purpose on Friday.
Thus, a woman who lights Shabbat candles two or three hours before sunset on Friday had not fulfilled the Mitzvah of lighting Shabbat candles and she may not recite a blessing on such a lighting.
However, the Gemara (Berachot 27a) states that Rav (the greatest of the Amoraim) would light Shabbat quite early and then pray Arvit of Shabbat. This seems puzzling since we have established that one may not light Shabbat candles too early on Friday afternoon.
In order to interpret this Gemara, the great Rishonim explain that although in general, one may not light Shabbat candles too early, if a woman accepts the sanctity of Shabbat upon herself immediately following candle-lighting (or if Kabbalat Shabbat is recited immediately after candle-lighting), it is then permissible to light candles earlier since it is now recognizable that this candle-lighting is being done in honor of Shabbat. Maran Ha’Shulchan Aruch (Chapter 263) rules likewise.
Nevertheless, even so, one may never light earlier than “Pelag Ha’Mincha,” i.e., one and a quarter seasonal hours before nightfall (some rule that it is calculated before sunset).
(The time for nightfall, i.e., “Tzet Ha’Kochavim”, can be found in most quality halachic calendars. Some list the time of “Pelag Ha’Mincha” as well. One who does not have such a calendar should calculate thirteen and a half seasonal minutes after sunset as nightfall. One and a quarter seasonal hours before nightfall is “Pelag Ha’Mincha”. “Seasonal hours” can be calculated by dividing the day from sunrise to sunset into twelve equal parts. Each one of these parts is a “seasonal hour”. Each seasonal hour contains sixty seasonal minutes such that, in the winter, these minutes are shorter than regular minutes and, in the summer, they are longer.
Summary: One should not light Shabbat candles too early; rather, Shabbat candles should be lit from approximately a half-hour before sunset. One who wishes to light earlier may do so from the time of “Pelag Ha’Mincha” which is one and a quarter seasonal hours before nightfall, provided that one accepts the sanctity of Shabbat immediately following candle-lighting.