It will depend on the amount of chests you buy, whether common or rare.
Based on 100 chests:
Maybe with good luck you can get about 10 energy.
Rare chests are even better, because there are chests where you can get up to 3 energy. In total, about 15 to 20 at least.
Interesting, thanks! As I said, I never worked with buying energy or something similiar.
You're welcome, I've been doing it to have a kind of "infinite energy". This gives me more possibilities to fight and, luckily, win more. But for it to work, I would have to have some things going right, like the amount of SPS among other things.