Floating solar PV systems are not a new technology, but the combination of fully commercialized technologies combined in new ways, for example, moored flat-bottom boats and solar photovoltaic systems, including panels, transmission and inverters from direct to alternating current. They offer a new place to install solar PV that does not conflict with habitation, agriculture or biodiversity as long as key marine environments are respected. There are two classes of opportunities: when the floating solar PV system is stand-alone; and when it is retrofitted to or built with a hydroelectric facility as a hybrid. Floating PV plants are more compact than land-based plants, their management is simpler and their construction and decommissioning straightforward. There are no permanent alterations to the landscape (e.g. concrete foundations), so their installation can be totally reversible. Floating solar PV adds energy capacity to existing hydroelectric dam facilities, while the dams offer dispatchability and the PV system can piggyback on existing transmission. As of the end of September 2018, the global cumulative installed capacity of floating solar PV plants totalled 1.1 GW. Demand for floating solar PV is expanding, especially on islands (and other land-constrained territories), as the cost of the water surface is generally lower than the cost of land. Floating solar is particularly well suited to Asia, where land is scarce but there are many hydroelectric dams with existing transmission infrastructure.