A method is provided, repeated over successive time slots, for controlling the distribution of power from a time varying renewable power source between a battery and a power grid. The method comprises comparing the maximum input power of a battery with the power output of the time varying power source and determining a ratio for distributing the power between the battery and the power grid based on the comparison. Wherein distributing the output power to the energy storage device as a priority when the output power of the power source is below the maximum input power of the energy storage device; and increasing the ratio for the grid and decreasing the ratio for the energy storage device as the output power of the power source increases above the maximum input power of the energy storage device. The surplus power produced by the power source, above the maximum input power of the energy storage device, is discarded when the output power is distributed to the energy storage device.