Abstract: Methods and systems for desalinating feedwater are disclosed. The system includes at least one feedwater source, a reverse osmosis module, an input feedwater stream fed to the reverse osmosis module, and a control module. The feedwater stream comprises water from at least one feedwater source, e.g., from two or more feedwater sources of different salinities. The control module analyzes the level of energy available to the system, and increases the salinity of the input feedwater stream proportional to an increase in available energy. Feedwater stream salinity can be adjusted to reach water demand targets and fully utilize variable power inputs from renewable sources.