Most lights in your home probably operate at 120V. If a facility has high-bay lights, those are probably supplied by 277V. These are known as “line-voltage” lighting products. Another family of lighting products are “low-voltage” (LV) lights.
The LED is really an LV light, though the screw-in “bulb” is a package that operates off the line voltage. LEDs aren’t the only type of LV lighting product. Incandescent and tungsten-halogen versions have been around for many years. That long time on the market means you have many lighting choices.
By definition, LV lighting operates at under 30V. The voltage level is typically 12V or 24V. Excluding LED, the output is under 25 lumens. With LED, you can get up around 150 to 180 lumens.
For our purposes here, we’re going to exclude LED from the discussion going forward. We’ll focus on traditional LV lighting. Now, why would you want the losses incurred by a transformer (to step down from 120V or 277V to 24V or 12V) only to get a weak lumen output? Would it not make more sense to just use line-voltage lights?
A clue is the fact that these are low-voltage. The low voltage makes them inherently safe. Another factor is that they have small filaments compared to their line-voltage counterparts. That permits optical control using only the lamp reflector, as opposed to needing shade and lens features. More of the light is focused in the beam, saving energy. The lamps tend to be shock-resistant, too.