Wave plants are currently extracting energy from sea waves at higher levelized cost of electricity (LCOE) compared to other renewable energy resources. The present research aims at reducing the LCOE of wave plants that use the axial flow Wells turbines as a power take-off system by optimizing the turbine rotor geometry. A novel rotor geometry was proposed, numerically investigated and optimized. This geometry was obtained by varying and optimizing the radial solidity distribution of the traditional Wells turbine rotors. Up to 15% saving of the Wells turbine LCOE was achieved by optimizing the rotor geometry. This cost saving is mainly due to the increase of the turbine output power where the change of the blade manufacturing cost is negligible. The present work highlights the significance of the plenum chamber turbine coupling for every turbine design. This is because the numerical results showed an increase of the damping coefficient for the turbine with the optimized rotor geometry. Therefore, it was necessary to reduce the plenum chamber volume in order to maintain an optimum turbine-chamber coupling. This increases the cost saving to 20.6% at the turbine design point and reduces the plant construction time. (C) 2016 Elsevier Ltd. All rights reserved.