This paper presents a blind adaptive carrier-phase offset recovery algorithm based on an output energy maximization approach for eight-level vestigial sideband (8-VSB) signals. Unlike conventional quadrature amplitude modulation signals, the 8-VSB signals in practice have an asymmetric energy balance between the in-phase and quadrature components, which can be used for recovering phase offset, but this has been neglected. We investigate this energy imbalance of the VSB signals and propose a blind adaptive phase offset recovery scheme by maximizing the energy of the in-phase component. Due to the maximum energy property, the proposed algorithm results in superior mean square error performance without undesirable local minima in comparison with the existing phase offset recovery algorithm based on dispersion minimization. We verify the performance of the proposed algorithm with a mathematical analysis and simulation.