One of the challenges in measuring efficiency with MR16 bulbs is that the waveforms have AC components, thus care must be exercised for correct measurement. A power meter (or a power source with built-in power measurement function) needs to be used to measure the average input power. The waveforms shown on the right side of this slide are the driver input waveforms powered by a Lightech LET75 ET at 120 VAC, 60 Hz, without a dimmer.