If we want to drive up to the Haleakala Mountain instead of joining a tour group for sunrise, what time do we need to get there? Thanks.

I would suggest no later than 5:00AM.
There is a building in which you can stand in if it's too cold outside. Make sure you walk around after the sun comes up. It is like being on another planet. If it's really clear you will be able to see both volcanoes on the Big Island!

The building is quite open & not heated, so dress warm! It's cold & windy up there, but definitely worth the trip!
Enjoy - Dianne

Don't underestimate how warmly you need to dress! I was freezing in pants, long sleeves, and a jacket, and we were there late morning.

Have fun!

Before 5am and if it is cloudy that is a major bummer.. It is so cold and usually you see people who have taken their bedspreads or blankets from the hotel to keep warm.. I have done it once and will not do it again but I am glad I did it but getting up at 2am to arrive at 5am after long days at the beach it throws the body out of whack for a couple of days but the good news is the Kula Lodge is excellent for breakfast or lunch!
Personally, I would do the tour group because it is very winding road and alot of fog and it is very early morning and they will probably have warm beverages and you can catch some extra sleep..just my opinion..
Have fun and take some hot beverages..