This study introduces a novel index that accounts for the interactions of wave climate and wave energy converters, offering an unbiased approach that considers climate variability, survivability and energy production. Application of the index is done with use of a long-term wave hindcast, validated database for the North Sea. A detailed overall and monthly wave resource assessment reveals that mean expected wave resource is ≈15 kW/m, with higher nearshore values in December-January ≈20-25 kW/m. Lower magnitudes are met in July with values closer to ≈ 4-6 kW/m, as a general observation higher resource magnitude is expected at upper parts of the North Sea, with diminishing levels towards the English channel, the difference in available resource is almost half. The region favours "smaller" capacity devices for energy production, with capacity factors having encouraging results. The highest mean value for a capacity factor in the region is 25-32%, depending on device. However, the new index indicated that the highest capacity factor value should not be the determinant parameter. In fact, other locations have less energy production annnually, but exhibit significantly less variation in production patterns, and lower extreme values of return waves.