If I want to replace sugar with honey in black or green tea, can I add the honey at any point or should I wait until the tea cools down a bit?
There is apparently evidence that some of the flavour compounds in honey deteriorate during heating:
The text suggests that honey should not be heated to more than 50 degrees Celsius (122 degrees Fahrenheit). So it might be wise to let the tea cool down a bit before adding the honey. Having said that, I usually put the honey in immediately after removing the tea leaves and it tastes fine to me. The flavour of the honey is clear and pronounced and I have never felt that anything was missing.
It is preferable to add the honey into the tea when it is hot to let it melt a bit. Otherwise, it'll be harder to mix it in. And yes, you can replace sugar with honey in tea. It is healthier and I do it all the time.
If you want to try something other than honey, agave nectar is another sweet alternative. I use it in baking instead of honey sometimes.
Some people are "iffy" as to this because it generally requires a lot more to sweeten than sugar, and can leave a residue if too much is present, but I actually generally prefer to sweeten my tea (and coffee) with honey and/or brown sugar.
Hmn... It's not the flavor that you should be worrying about when adding honey to hot tea, but rather, the honey's natural antibiotic properties. At high temperatures, the enzymes are destroyed.
Well, the thing asks that I avoid making statements based on my opinion... So I'd like to claim right here that this is not my opinion. I study food technology and honey was a topic that was discussed. And also, I was holding a conversation with the guy selling Manuka honey. So although I can't back up my words, I'll provide a link with information on honey.
"But, in some cases, the peroxide activity in honey can be destroyed easily by heat or the presence of catalase." - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3609166/
Yes, honey is great in tea. Honey from different flowers can taste quite different so it could be fun to experiment with different types of honey and see which tastes good to you as that's such a personal preference. One honey which markets itself as 'drinking honey' is Belixir Drinking Honey which is targeting people who like honey in tea or in other drinks.