Aruch haShulchan O"C 514:19 writes "A Ner Shel B'teilah is when you 
don't need the light at all. But if you want to add much more light 
(l'hosif ohr harbeh), that is certainly mutar, and is Oneg Yom 
Tov..." Regarding neros in shul, he writes there, "It is for Kavod 
HaTzibur, and everyone is noheg to allow it. Nevertheless, you should 
warn them not to have overly many (shelo l'harbos harbeh), especially 
on the day of Hazkaras Neshamos, when they do infinitely many 
(she'marbin bli shiur), and you should stop them from this."

>From this language, it sounds to me that the AhS believes that while 
in general more light is more oneg, it can reach a point where there 
is so much light that additional candles are considered Shel Batalah. 
This is extremely similar to Rav SZ Auerbach's comment (Shmiras 
Shabbos K'Hilchasa 43:(171)) that when electric lights are already 
on, Neros Yom Tov add no extra simcha whatsoever.

Okay, let's turn to the Chofetz Chaim. Mishneh Brura 514:30 writes 
that when having a bris (which is obviously during the daytime), even 
if it is at home, one may light candles, because it is for "kavod and 
chivuv mitzvah". Similarly, he writes in 514:31 that candles may be 
lit in shul even during the day, because it is for the kavod of the 
place.

He discusses Yahr Zeit candles in the Beur Halacha there, "Ner Shel 
Batalah". He offers four ideas. I'll list them in the same order that 
he gives them, but I'll number them with what seems to be his 
preference:

1) Light it on Erev Yom Tov.
3) If it wasn't lit on Erev Yom Tov, light it in the dining room, so 
as to get additional dining light.
2) But even better is to light it in shul, which solves any chashash 
of ner shel batalah
4) B'shaas had'chak, we can allow it anyway, because it is sort of 
("ke'ayn") a ner shel mitzvah, being that it is to honor his parents.

I find it noteworthy that even in this worst-case scenario, he still 
allows lighting the yahrzeit light, even though it is NOT a "ner shel 
mitzvah", but is only "ke'ayn ner shel mitzvah".

But now I am even more confused than before, because by Bedikas 
Chometz, in the worst-case scenario, the Chofetz Chaim (Shaar 
Hatziyun 435:9) advises delaying the bedikah to Chol Hamoed, rather 
than lighting a ner for it on Yom Tov. He seems to be saying that 
lighting a yahrzeit candle on the day of the yahrzeit is a bigger 
mitzvah than using a ner to do a bedikas chometz as soon as he 
remembers. Wow, I never realized that yahrzeit candles were that 
important.

And Rav SZ Auerbach (presuming that he agreed with Beur Halacha 
514:Ner) would seem to be saying that even though the general rule is 
that lots of lights means more oneg, the extra hidur of using an 
avukah for havdala is not as big a deal as yahrzeit lights. Okay, but 
I wonder why.

Akiva Miller