The advantages of combining offshore wind and wave energy into a single farm include reduced hours of zero power output and reduced inter-hour variability. Both advantages facilitate grid integration of variable renewables. The power output profile of a combined farm is substantially different from a 100% offshore wind energy farm or a 100% wave energy farm. The different power output profile of combined farms with a higher frequency of hourly power output near the annual capacity factor potentially allows a reduction in the capacity of the offshore transmission system. The transmission capacity reduction is balanced by the curtailment of energy during the few hours a year that a combined farm generates at full power. An optimization of the transmission capacity for various generation mixes of wind and wave was investigated, and results show that the optimal transmission capacity for a 1000 MW combined farm is approximately 80 MW less than either a 100% wind or 100% wave energy farm.