High- and medium grade green tea (especially the Japanese varieties) have significant amounts of L-theanine, which has its own effects and synergies with caffeine. For me, the same amount of caffeine will have me anxious and give me tunnel-vision if I get it from coffee while more euphoric and peppy if from green tea.

What should we be feeling with L-theanine?

I never found it affected me.

With good green tea that has lots of it (shaded tea, but doesn't need to be gyokuro, Sencha Momiji is my favorite, cold brewed over night, then strained in a french press), I usually feel a slow but steady rise in wakefulness and around the time where I would start to get jittery (say, like when drinking a few too many cokes), it transitions over to an incredible calm mixed with a feeling of... wideness. Like your FOV is actually expanded by a few degrees, on many levels. Close your eyes and it feels like being at peace in a kind of Zen state. But... with a little buzz, very much an eager, productive peace where things line up and you can approach them.

It's probably different for different people, but I can highly recommend trying to "get some good stuff" to see whether it can do the same for you. I wouldn't want to miss it.

This!

Another curious thing I have noted: While living in Japan I was binging on houjicha[0] (which has significantly less caffeine due to the roasting process) on late evenings so I would still be able to sleep. After several strong pots (we are talking litres of 1:1 water/leaf ration) I would often get into a different mind-space that is pretty close to what you are talking about. I tried to research if other catechins (like l-theanine) also disappear in the roasting process or if they could be the explanation, but weren't able to find anything to back this up.

0: https://en.wikipedia.org/wiki/H%C5%8Djicha

I haven't really taken it as a supplement/extract by itself, but drinking lots of strong green tea gives me distinct but different effect from coffee/energy drinks/caffeine pills.

It mostly seems to negate the negative effects of caffeine (apart from problems falling asleep) and gives a mood-boost and counteracting stress. It only goes so far of course, over-consumption of tea will still yield anxiety and dependence, but the threshold for this is a lot higher.

Can't help with the caffeine content, but I agree that there's a vast difference between good and bad tea. I particularly detest places that use a teabag and add milk before removing the bag.

As George Orwell put it, "the best manner of making it is the subject of violent disputes" http://www.booksatoz.com/witsend/tea/orwell.htm

What's the issue with adding the milk before removing the bag?

The tea keeps brewing, but this time in the milky water. Tea brewed in milk is noticeably different to that brewed only in water. This can be done deliberately (eg, when making Masala Chai), but it's not normal (nor, in my book, acceptable) for tea to which milk is added later.

Yeah, there is a whole subjective component to all of this that is hard to get good information on.

I am older, and drink both tea and coffee depending on mood, need for caffeine, etc.

There are some online guides that give ratios of caffeine in typical tea versus typical coffee. Of course, figuring out what "typical" is is the issue! What I've seen shows that black tea has quite a bit less caffeine per serving (bag, infuser full, etc): 1/10 to 1/5 of coffee caffeine. However, there seems to be a big difference in coffee strength! As an anecdote, I personally find little difference in caffeine between weak coffee (Dunkin Donuts regular is a good example) and a strong black tea (Tazo Awake, for example). On the other hand, Starbucks drip coffee is like getting a meth injection! Immediate symptoms: increased heartbeat, "speedy" feeling, fidgeting, etc.

Also, I hear you on water temps. At home I use an aeropress and 195 degree(F) water for coffee pressing. To me, there really is a taste difference (less bitterness, mainly) if I leave the water just below boiling, but some people don't see any difference and like their water hotter.

Experimentation seems to be the only way to get to your caffeine happy place!

Starbucks drip is absolutely crazy. I always feel awful if I drink on an empty stomach.

Here's some data from various sources regarding caffeine levels in different types of tea, and also some data about extraction:

Theanine and Caffeine Content of Infusions Prepared from Commercial Tea Samples https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4787341/

Caffeine in Tea Revisited http://teaintheancientworld.blogspot.com/2017/06/caffeine-in...

Caffeine Content in 39 Tea Samples https://www.teaguardian.com/tea-health/caffeine-content-39-t...

90% of the tea I drink is loose-leaf, and I'm sure there are definite differences between loose and tea bags, because tea bags very often have very fine almost tea "dust" instead of actual leaves, and the increased surface area makes it extract faster.

The psychoactive effects you are talking about are likely a result of L-Theanine, if I had to guess

I don't know how to calculate amounts of caffeine but regarding the differing psychoactive effects, Googling 'tea stimulants' will get you lots of info... seems the main other stimulants in tea besides caffeine are theobromine (as found in cacao/chocolate) and theophylline.

The real question isn't how much caffeine do the tea leaves contain, but how much of it migrates into the water during steeping. My understanding is that the preparation of the tea (drying process, water temperature, steeping time, first vs second infusion, etc) has as much to do with the final caffeine content as the leaves themselves.

That is interesting about the thermometer! I noticed my tea always tastes like ass if I use boiling water, so now I add a bit of cold water after it boils. What is the optimum temperature?

It depends on the tee. Most green tea advises to use 70°C water.

A good approximation of that is taking 2/3 boiling water and 1/3 tap water (if you have 10°C tap water that works out to exactly 70°C). Don't forget stirring before adding it to tea, to make sure it's well mixed.

For optimal results obviously read the packaging of your tea and use a thermometer.

We have a kettle that can be set to temperatures between 60°C and 100°C. I cannot recommend this enough.

Where can I get/try good tea? Order online? Any recommendations?