I have a number of small lamps that use 12V halogen bulbs, either 10W or 20W G4 types. Each lamp has a 12V step down, wall-wart style transformer with te on/off switch in the low power side of the circuit. I want to change to LED bulbs instead of the G4 halogens but must I also change the transformers for LED driver modules? The LED bulbs I have are AC/DC and seem to work OK with the transformer output. How much power is the transformer taking when the bulb is switched off and will I save very much by switching to an LED driver that is only turned on from the mains side of the circuit. My "smart" electricity meter tells me that a 12V transformer plugged in, but with the lamp switched off, hardly takes any power at all - is this true?