Everyone starts the season with 10 energy. It requires 1 energy to start a ranked battle. You regenerate 1 energy every 60 minutes.
Your default starting energy capacity is 20. Any energy regenerated while your capacity is full will be lost.
There are two energy improvements that can be purchased using KKT:
+10 capacity addon: Energy capacity addons are lifetime and are not lost at the end of the season.
x2 energy boost: Enjoy double energy regeneration for the whole season!