This article investigates the impact on power production of an energy ship of two types of heading controllers. The first controller includes a filter which eliminates the wave-frequency dependent motion of the ship, while the other aims at compensating the effects of waves on the motion of the ship. The study is based on a numerical model of the energy ship which is presented in the paper. Results show that waves compensation reduces the generated power variation but increases rudder oscillations. In the opposite, the waves filtering controller allows for a slightly greater power production at the expense of greater power variations.