Popularly called the zero watt bulb, more appropriately it is intended as a zero watt-hour appliance. Yes, it does consume some power -- but not so much as to turn the motor action in the domestic energy meter that faithfully records the electricity consumption. So its use can go unnoticed. It may be okay to assume one bulb in isolation may hide the consumption. But a combined use with many such or other devices at the same time will spill the beans -- the zero watt hour bulb can not live up to its reputation but will cause register its incremental effect on the power bill!