It would be great if either the energy cost of each fight was reduced or better yet if you only lost energy if you lose the fight. It's a great game but it's really annoying having to wait after every other battle.
The more fighters you collect, the less energy will impede you. On top of that, as Diony said, you can unlock the energy nodes of a fighter to have them recharge twice as quickly too.
The energy limitation is to keep you from using the same team over and over, so try to collect and train more varied fighters, then you won't have as many problems with energy