Wind speeds are often low in periods (summer, eventually) when the sun resources are at their best. On the other hand, the wind is often stronger in seasons (the winter, in many cases…) when there are less sun resources. That can make solar-wind hybrid solutions an alternative to consider.

Even during the same day, in many regions worldwide or in some periods of the year, there are different and opposite wind and solar resource patterns. And those different patterns can make the hybrid systems the best option for electricity production.

The combination involved on hybrid systems is rather obvious: to get a target goal of, say, 120 kWh of electricity per month we can use a single 3kW wind turbine (instead of a 6kW one...) and a solar system with a smaller array of modules.

An hybrid wind-solar electric system demands an higher initial investment than single larger systems: large wind and solar PV systems are proportionally cheaper than two smaller systems...

But the hybrid solution is the best option whenever there is a significant improvement in terms of output and efficiency - which happens when the sun and the wind resources have opposite cycles and intensities during the same day or in some seasons.

http://www.house-energy.com/Wind/Hybrid.htm