No, an efficient transformer cannot step up energy because that would violate the law of conservation of energy.

Can a good transformer step up energy?

Can an efficient transformer step up energy? ... No; there is no such thing as an "efficient transformer." No; energy is conserved and cannot be stepped up.

How efficient are step up transformers?

Some transformers even provide a variable output by allowing connection to be made at different points on the secondary coil. A step-up transformer is one that increases voltage, whereas a step-down transformer decreases voltage. ... This is nearly true in practice—transformer efficiency often exceeds 99%.