In this paper, the use of a seawater desalination system as a controllable load is proposed to compensate the power fluctuation of renewable energy sources and control methods are discussed. On/Off control tests were conducted with the actual desalination system without a power converter and variable pump speed tests were conducted with a experimental desalination system with a power converter. The On/Off control turned out to be not so useful for power quality enhancement. With a power converter, the power consumption of the system can be controlled with enough accuracy and response speed for the suppression of the power fluctuations caused by wind turbines and photovoltaic cells.