How to Choose a Low Voltage Transformer in 4 Steps

It’s our mission to make choosing a transformer as easy as choosing from a box of chocolates.

A couple months ago, I promised to write more “how-to” posts here since they seem to be most popular among all of you wonderful readers. Since then, I’ve posted How To Light a Foyer, How To Wash a Wall With Light, How To Choose a Recessed Shower Light, and How To Prevent a Power Outage Blackout.

Today, I’m tackling an arguably drier topic. However, for those of you that are diving into remodeling projects for the New Year, it’s a crucial one.

First, an introduction for those not familiar with transformers in the lighting industry (Hint: they are not shape-shifting creatures). There are two types of lighting systems: Line voltage and low voltage. Line voltage simply means that your lighting fixtures may be plugged in directly to an electrical outlet or hardwired directly to a power source. The voltage that  the light fixture needs is the same as the voltage supplied from your wall. Low voltage lighting systems require lower voltage to operate than the typical power source supplies. So, if the power source in your wall outputs 120 volts, low voltage lighting fixtures require an input of just 12 or 24 volts. That’s why you need a low voltage transformer – to convert the voltage from your power source to the amount your lighting fixture needs!

Occasionally, the transformer is built right in to the lighting fixture – in which case there’s no need for this guide. The decision has been made for you! However, if the transformer is separate, you’ll need to make sure it is compatible with your lighting fixtures. Follow this guide to make your selection in four steps …

Decision 1: Volts

Low voltage lighting systems operate on either 12 or 24 volts. The easiest way to start filtering out the right transformer is to determine if the low voltage light fixture you need to power requires 12 or 24 volts. You should be able to find this information in the description/specifications of any product. Also, determine whether your power source outputs 120 or 277 volts. Most power sources in the U.S. output 120 volts, but there are transformers available for power sources that output 270.

Decision 2: Magnetic v. Electronic

There are a few pros and cons to consider here. Electronic transformers have an additional electronic device called an inverter that enables them to be much smaller than magnetic transformers. So, if you need to tuck the transformer into a tight space, you might want to veer toward an electronic transformer. Another advantage to an electronic transformer is that it can be reset at the wall switch if there’s an overload.

Although magnetic transformers are somewhat larger and heavier, they are more durable than electronic transformers and they tend to last longer.

Decision 3: Wattage

Now that you’ve determined whether you’re looking for a 12-volt magnetic transformer, 24-volt electronic transformer, 12-volt electronic transformer, or 24-volt magnetic transformer (that’s a mouthful!), you can narrow it down by wattage. Each transformer has a “maximum wattage load.” Typically, this is what the actual product is labeled. The rule here is that the maximum wattage load of your transformer must be equal to or larger than the total wattage of all the light fixtures you are connecting to it. Let’s say you have one light fixture with one 60-watt light bulb for the transformer mentioned above. That’s fine. However, if you install a light fixture with three 60-watt light bulbs, you’ll need a transformer with a maximum wattage load of at least 180 watts.

Decision 4: Enclosure

If you see the word “enclosed” in any of the product descriptions, this simply means the transformer is encased in a metal case that provides storage space for terminal block connections you may need to make. It’s fine to choose a transformer that’s not enclosed, but you should probably store it in some sort of metal housing (i.e., a junction box).

As always, please feel free to ask any questions here on the blog or by calling our toll free customer service number!

Emily Widle

Emily Widle

Emily graduated from UNC Chapel Hill with a degree in journalism. She enjoys scouring the news to report on the latest in the lighting industry as well as bringing valuable remodeling tips and exemplar home projects to light.

  • Lighting Service

    For the reasons you started above, I prefer electric transformers over magnetic. :)

  • Michael Dunn

    What you did not discuss (which unfortunately is what im looking for info on) is whether you should choose a transformer with AC or DC output…. I think this may depend on your setup, as an AC output might have addl line loss, etc… Any thoughts on this?

    • Jacob from Pegasus Lighting

      DC electronic transformers are ideal for longer runs because they alleviate voltage drop issues.

      DC transformers for use with halogen/xenon lights are very difficult to find these days. In today’s lighting climate, we most often see DC power supplies (called drivers) with LED lighting systems.