I live off grid so I have been installing lots of 12 volt lights but there are many other reasons 12 volt lighting makes sense, whether you have a grid connection or not. As my main battery system is 24 volts, not 12, there is actually little difference between having 12 volt lights in my environment or where 120 or 240 volts AC is the main power source.

First, the most efficient lighting available today use light emitting diodes, LEDs. LEDs are low-voltage devices, operating on approximately three volts each. Individual LEDs, combined in series-parallel configurations combined with at least a current limiting resistor and possibly an electronic regulator make up each bulb. Realistically, LED-based lighting can be ten or more times more efficient than incandescent lights. Additionally, they have lives 25 to 100 times longer.

If you can get past "the livingroom must be bright all over" and such concepts, there is a lot more energy to save as well. If you are in the livingroom watching TV, for example, somewhere between zero and five watts of light will be sufficient. If you are reading, you will need a bright light source but that does not mean you need to light the entire room at the same level. An LED-based light in the one to five watt range will be more than sufficient to use as a reading light.

That's the energy-saving side but there are other advantages to 12 volt lighting. They include safety, regulation and cost. On the safety end, 12 volts touching your skin is not dangerous. Thus, you can confidently work on circuits without danger of electrical shock. Regulation systems actually offer two advantages: voltage regulation itself and current limiting. The voltage regulation side means that your lights don't flicker when you start a high-current electric motor or such. They remain at constant brightness. In my case, with the primary battery system operating at nominally 24 volts, the step-down regulator isolates the lighting circuit from the state of charge of the batteries.

Additionally, most regulators include current limiting. What this means is that a short circuit just results in the voltage dropping to zero until the situation is corrected rather than a tripped circuit breaker or blown fuse. This feature along with the non-dangerous low voltage makes it a lot easier to confidently work on live circuits.

Finally, because lights for automobiles are 12 volts, the market is getting flooded with low-cost LED replacement bulbs for autos. Thus, an auto brake light or backup light bulb can be used to make very inexpensive reading and work lamps.

If you live in a 120 volt AC only house, you are going to need a source of 12 volts DC. There are inexpensive power supplies complete with regulation and current limiting available—the kinds designed to run, for example, a two-way radio. Another approach is a small battery and a float charger. If you have unreliable 120 volt AC service, this second approach will mean you have lights when the AC power is off.

I am a satisfied customer of 12 volt lighting. Even if you are on-grid, you could also be very happy with 12 volt lighting.