A transformer is a box which takes in electricity at X volts and puts out electricity at Y volts.   In fact, by the laws of physics voltage isn’t the only thing a transformer changes. In brief, when voltage is stepped down, current steps up and vice versa. However, that can safely be set aside for now. There are two main issues in selecting outdoor lighting transformers. First, they’re used to reduce the voltage of house current from 120v to either 12v or 24v. Output voltage must match the fixtures. Second, the transformer’s capacity must be adequate.


Safety is one of the top benefits of low-voltage current. After all, the outdoors is a less controlled environment than interiors are. With wiring running all over a property, unpredictable events can expose them. Weather, animal activity, landscaping work, and play all can increase the chance of a person contacting a wire. The risk of harmful electric shock from 12 volts is tiny A shock from 120v house current can be fatal.

Economy is another benefit of stepping 120v house current down to 12v for outdoor lighting. A system with low-voltage LEDs uses much less electricity to produce a given amount of light. Of course, LED fixtures and bulbs are more costly to buy than conventional equivalents. However, they last much longer. The power savings and longer lifetimes are a financial winner.


The first criterion in transformer selection is the electrical demand of the lighting system. The right voltage for the fixtures (12v or 24v) is a must. Next, the transformer needs to have enough output capacity (in watts) to supply the system. The designer has to compute the power demand of the design. Basically, this estimate accounts for the total wattage of the planned fixtures, plus some extra due to loss. No electrical system is perfectly efficient. Wiring layout and other factors waste some of the power. Some of the power coming out of a transformer never makes it to the bulbs. However, a skilled designer can accurately estimate the loss in a design. This enables the choice of a transformer big enough so the system, with loss, won’t pull more than 80% of its capacity.


Houston Lightscapes also makes it a practice to pick transformers that are future-proof and aesthetic. In calculating the right wattage, it’s smart to allow a margin for changes in the system design. For instance, adding more or bigger fixtures. Where the layout of a property makes situating the transformer challenging, there are compact electronic transformers available as solutions. Selecting transformers for outdoor lighting designs isn’t a guessing game.  The right choice by an experienced pro is a long-term winner for any homeowner.


The team at Houston Lightscapes takes pride in their many years of experience in the landscape lighting industry. They've been serving the greater Houston area for over 30 years bringing innovation and elegance to their designs. Learn more about Houston Lightscapes here.