The energy of a digraph $D$ with eigenvalues $z_1,z_2,\ldots,z_n$ is defined as $E(D)=\sum\limits_{j=1}^n|\Re z_j|$, where $\Re z_j$ is the real part of the complex number $z_j$. In this paper, we characterize some positive reals that cannot be the energy of a digraph. We also obtain a sharp lower bound for the energy of strongly connected digraphs.