In PvP one of the largest determining factors for success is how fast you can launch a charge move. Launching charge moves sooner than your opponent can not only allow you to get the KO in but can also bait their shields effectively lowering their ability to withstand your Pokemon’s more powerful, higher energy cost moves.
The table below features each species highest energy gaining fast move combined with their lowest energy cost charge move to give a clear working idea of their threat and utility. Only these two attacks are chosen for the sake of simplicity. To find out the activation time of any combination, just divide the energy cost of the attack in question by the energy per turn.
Activation Time = C.Move Energy Cost / (F.Move Energy / (F.Move Duration +1))