A grid tied inverter, system and method

A grid tied inverter comprising an unfolding circuit connectable to an electricity grid; and a DC to DC current fed converter operable to generate a current waveform from a battery, the current waveform being substantially synchronised to the electricity grid, wherein the unfolding circuit is operable, in a first mode, to convert the current into a sinusoidal waveform have an instantaneous voltage suitable for injection onto the grid.