I'm not sure, there's some controversy regarding this. Green tea and black tea are the same thing, only the black tea is roasted/fermented/painted/whatever. So on the one hand, don't be fooled by the fact that it's green, but on the other, that's what I've been told. I.E. it's probably an oversimplification, and is more complex than that.
To tell you the truth, it doesn't feel as caffeinated as even regular tea, I have no idea why. If I drink enough, late, it will keep me up. So I don't, but I can get away with a little.
I'm not sure what your goals are, but if you want to cut down without giving up caffeine, it's the perfect solution. If you want that "jolt", look elsewhere.
I would recommend the following: get plenty of sleep, drink lots of water, get some regular activity (exercise), start the day with protein, and don't forget to breathe. In other words, then you won't need the jolt.