I find it strange when people use this phrase, since energy can't be produced, only converted to another form of energy
Isn't producing usually converting one thing to another?
(I guess "elektryczną" is missing?)
I agree. Adding 'elektriczną' makes this about a specific form of energy thus implying conversion. In my opinion just 'energia' is a too abstract concept to be used with this verb. But I guess it's a matter of personal preference