What is the Difference between Low Voltage and Line Voltage?

Low Voltage vs. Line Voltage

     There are two primary types of landscape lighting systems: low voltage (12 volt DC) and line voltage (120 volt AC). The most common type used in residential applications is low voltage, but there are many commercial systems that also utilize low voltage.  Low voltage is as the name implies, characterized by an output of 12 volts, but many fixtures will operate in the 8-15 volt range (especially LED landscape lights). On the other side line voltage operates in the range of 110-120 volts. A low voltage system typically won't shock you if you happen to touch an energized wire and close an open circuit. This is one of the reasons low voltage is used in most applications, but there are many reasons for its popularity.

    Line voltage on the other hand is what the power company sends you that powers most of the light fixtures (and everything else) in your home. We've all been zapped at one point or another so we know what line voltage is capable of - be careful! The other major difference between the two is that low voltage is a direct current whereas line voltage is an alternating current. While this is not really that important it will help in understanding how the transformer works. Just as there are numerous choices in lights there are also many different transformers. Pictured below is a Vista stainless steel transformer with a digital timer. I have used this transformer in various wattages (300-600-900-1200) and it has proven to be a quality transformer.

Landscape Lighting Transformers

     In a line voltage landscape lighting system you do not need a transformer. However, in a low voltage system a transformer is required. The transformer that you plug into the outlet "transforms" the 120 volt AC from the receptacle into 12 volt DC which then goes on to power your lights. Transformers come in a myriad of wattage amounts, from 15 to 1200 watts and everything in between. Here is where LED landscape lights really shine (no pun intended, honest). Since LEDs draw only about 70% of the power of typical incandescent bulbs you are able to use a much smaller transformer for the same amount of lights. In fact, I recently updated an incandescent system to an LED system by changing all the fixtures over to LED (I changed the entire fixture, not just the bulbs). Before the switch, the system used three separate transformers for just over 60 spot lights. After the LED update, we were able to use only one transformer and even added another 25 hardscape lights! View this landscape lighting job at the Elemental Landscapes website.

Pictured here is a small wattage Malibu transformer. While their lights are not up to my standards this transformer is ideal for small systems or individual landscape light circuits.

I especially like this one because you can run into the local big box and pick one up fast.  In the next article I'll discuss transformers in more detail. We'll cover timers, circuits, variable voltage taps, and more.