Low-voltage outdoor lighting uses 12 volt instead of the common household 110/120 volts. But do not be confused: low-voltage doesn't mean low energy consumption...
Low-voltage (12 volt) outdoor lighting systems are cheap and easy to install, and a common option to illuminate walkways, gardens and building exteriors and architectural details, but you should pay attention to their consumption.
Low-Voltage & Energy Performance
Many people confuse low-voltage with low-wattage, but the truth is: a low-voltage system can actually be an energy waster.
»»» Low-voltage systems doesn't mean low-energy consumption.
»»» Their efficiency
depends on the type of lamps and lighting controls used with them.
»»» Use CFL and LED for huge energy savings.
»»» Do not use incandescent lamps;
»»» Do not also use halogen lamps, unless the lights are going to be on for short periods.
»»» Use timers and photocell systems to reduce energy consumption.
And that means that the energy-efficiency of a low-voltage system depends largely on the type of lamps used in it, and their wattage; and that you should use lighting controls (timers, photocells...) to get significant energy savings.
Low-Voltage Outdoor Kits
Pre-packaged low-voltage kits comprise a transformer (or power back), a timer, cables and lights for complete installation. These kits are typically modular, i.e., they are designed to be expanded: you can add lights in a later time, or purchase a second (and a third…) kit to expand a previous one. These kits are geared to the do-it-yourselfer.
Prices and Quality
There are many inexpensive low-voltage kits (with prices that range from $15 to $100), but the best kits may cost you $300 and more, depending on the number of lights, features and quality.
Kits using compact fluorescent (CFL) and LED (Light Emitting Diodes) lights are more expensive than those using halogen bulbs, but they are worth every penny (unless the lights are off most of the time).
Halogen kits (typically using 4 to 7 watts lamps) are very common, but kits with LEDs and CFL lamps are a better option for lights that are going to be on for significant periods (say, more than 20 minutes/day).
Be aware with the quality of low-voltage products.
They may involve higher initial costs, but they will last longer, and will provide significant energy savings and will be more environmentally-friendly.
Do not forget that outdoor lighting products should be water-resistant and rated for outdoor use. Waterproof and corrosion resistance are very important for durability.
Transformers (Power-Backs) And Outlets
Low-voltage transformers are designed to reduce the 110/120 household line voltage to an output voltage of 12 volts, by simply plugging them into standard outdoor or indoor outlets.
Most transformers, even the cheaper ones, have automatic timers in order to switch lights on/off at preset times.
The number of lights
The number of lights that can be connected to the transformer varies with the capacity of the transformer and the wattage and type of the lamps. If the transformer is, say, 100-watt, then the total wattage of the lights should not exceed 100 watts (20 garden lights with 5-watt bulbs, for instance).
So, take into consideration the type of lamps and their wattage. Do not forget that LED and CFL (Compact Fluorescent Lights) provide, for the same wattage, about four times more light output than traditional incandescent lamps and about 2 times more than halogen lights. In other words: a 1-watt LED lamp produces as much light as a 4-watts incandescent lamp.
Low Voltage Cable
Low-voltage cable must be weather-resistant. Popular sizes include 12-, 14- and 16-gauge. Typically, 16-gauge cable carries 150 watts, 14-gauge cable carries 200 watts and 12-gauge - the standard - carries 300 watts.
Installation & Low-Voltage Outdoor Lighting
As mentioned above, pre-packaged low-voltage systems are relatively simple and safe to install, and geared to the do-it-yourselfer.