I agree on the energy, especially if you're hungry! My husband alternates green smoothies and (homemade) kefir smoothies every other day for himself and the kids (they LOVE them!!). I don't like his green smoothies because he puts a ton of funky fruit in them and I like mine very smooth and mild. I've been making the same one for myself for over a week and I'm not tired of it yet:
1 head romaine or ~4 leaves kale with stems removed
1-1.5 c frozen strawberries
~1 c ice water
It makes roughly 4-5 cups of smoothie, which is a good lunch or breakfast for me.
My husband's green smoothies include several different greens from his garden (kale, collard greens, swiss chard) and pineapple, bananas, oranges, frozen berries, spirulina, ground flax, grapefruit, etc. (whatever fruit he can find to stuff in there), usually with some stevia added for sweetness.