Not all drones use energy to fire though.
Also, knowing how much energy your drone uses will help to calculate your tactics.

Since my mechs also use energy shield, they are set up with physical and heat weapons, thus highly decreasing the chance that my energy using drone may deplete my energy shield.

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Aeacus

Sorry, but I think it is part of knowing your build and have a strategy to make that build work. The in game mechanics work fine in this area. If your running out of energy you likely need to tinker and change a weapon to heat or if using energy shields then use a non-energy drone.

Always read the drone properly before buying it. On my turns, I always look at how much heat and energy I have before using a weapon or activating a drone.