Removing ballast covers?

I am an a pretty experienced grower posting here because cannabis.com web site is down about 40% of the time.

Anyway in my Grow Bibile is always shows the metal case removed from the ballast. Growers that have like 6 ballasts seem to always take off the case and mount them on the wall.

Does removing the case save any power due to the fact that you can cool them better? If that's no why them tell me please.

No metal case would mean cooler running due to better air circulation and ventilation to the components, increasing reliability, but open components increase the risk of accidental damage or harm to yourself. do at your own risk. It's just a box of electronics at the end of the day.