Most of the inverters require input power to function, for safety reasons, I suppose. However, I install a two pole contactor with the coil powered by the normal source. If utility power drops off line, the contactor de-energizes and disconnects the invertor from the grid. I don't like to rely on electronics to keep people safe. There is also the issue of a disconnect at the point where the power enters the structure and labeling indicating multiple sources of power at the panelboard.
