This paper examines the optimum power output of a pitching-surge point absorber wave energy converter in irregular wave climates. A mathematical model based on frequency domain is used as the first step to estimate the hydrodynamic parameters of the device and its potential power output in realistic sea waves. The numerical results predict that the point absorber energy converter has the potential to absorb more energy than what is contained in its own geometrical width. The optimum power of the device is then obtained from wave tank experiments in irregular wave climates. The comparison of numerical and experimental results demonstrates that the frequency domain method based on linear theory will lead to an overestimation of the energy absorption for this device. The frequency domain method provides an upper estimate for wave energy absorption due to the non-linear, viscous effects and constrained amplitude of device oscillation. However, comparison of the performance of the device with other point absorber wave energy converters shows that this wave energy converter is one of the most efficient in terms of absorbing wave energy.