The idea for this one is to pick your favourite Christmas carol and repurpose it for your out-of-office response. It’s festive and sure to get a laugh! (Whatever you do, just don’t pick Baby It’s Cold Outside).
Walk through your office and take a look at your electronics and other potential energy drains. Since you will not be in the office, there is no reason to pay for electricity that you are not using. Make sure that you handle your shutdown properly.

I’m mostly back in my actual office now, but I went with “away from my computer between X and Z” a couple of times and just straight up “I am on annual leave between X and Z” a couple of times.
I wouldn’t be offended or consider saying anything to anyone who included this in their out of office message, but even as someone who is in a religion that forbids use of electronics on most holidays, I still think this message is 1) TMI; 2) doesn’t convey what it needs to convey unless you are explaining that you don’t use electronics during holidays, in which case you can just include that you won’t be checking email without including the religious explanation; 3) would come across to me as inclusion of personal information I don’t need, which would therefore strike an unprofessional tone,and I wouldn’t understand why you felt the need to include that info. How about “I’m out of the office without access to internet or email until (date). If you need assistance before this date, please contact…” Like I said, I think your colleagues are overreacting, but in general I would advise to leave all personal information out of your auto-reply — vacation, medical leave, religious observance, etc. — people do not need to know why you are out.