Energy can be stored by directing fluid into an expandable receptacle that has a relatively heavy mass above it. The fluid fills the receptacle such that it expands and lifts up the heavy mass above it. At a time when energy is needed, the fluid can be allowed to flow out of the receptacle and through a turbine or hydraulic motor to generate power or electricity. Intermittent or unreliable sources of power can be used to fill the receptacle, or power from a power grid can be used to fill the receptacle at times that are off-peak. During peak-load times, the potential energy of the fluid in the receptacle can be converted to power. The receptacle can also be used to control water flows and can provide a source of power and potable water to a community.