A number of renewable electricity technologies, such as wind, wave, tidal, solar, and run-of-river hydro share a characteristic that distinguishes them from conventional power plants: their output varies according to the availability of the resource.

This is commonly perceived to be challenging at high shares, but there is no intrinsic, technical ceiling to variable renewables’ potential. Variability has to be looked at in the context of power system flexibility: if a power system is sufficiently flexible, in terms of power production, load management, interconnection and storage, the importance of the variability aspect is reduced.