Landscape lighting transformer basics

12 volt lighting is like magic. You’re taking regular household line voltage and stepping it down to something that’s much safer and easier to work with. A rough knowledge of landscape lighting transformer basics will help you plan your system, if you’re a DIY-er, or it can help you understand what you’re getting if you’re hiring someone for professional outdoor lighting design.

What is a landscape lighting transformer?

landscape lighting transformer

A landscape lighting transformer typically consists of a weatherproof enclosure that contains electrical elements that take regular household current and decrease the voltage, typically to 12 volts. Your transformer plugs into a standard outlet (GFCI if outside or in an area that may get wet). Landscape lighting wire is connected to taps inside the box, and that’s what powers your lighting system.

Single vs multi-tap

The cheap transformers you can buy at the big-box hardware chains are most often single-tap transformers. That means that there’s only room for one wire to come into the transformer and connect to power. That’s fine if you have a short run of only a few lights, but that single tap greatly limits your flexibility.

Multi-tap transformers allow you to run multiple lines from one transformer. This is especially useful if you have a lot of fixtures, or if you have some long, long runs. Why would the length of the run matter? Voltage drop.

Put as simply as possible, voltage drop means that you’re not going to have the same voltage at the end of a run that you do at the start (at the landscape lighting transformer). Where does the voltage go? On any circuit, impedance is going to cause a reduction in voltage as you go down the line. It’s like water in a pipe – the farther from the source, the more the water pressure drops.

There are ways to deal with voltage drop. The best way is to use a voltage drop calculator (there are a gazillion online) and math it out. You can also play it safe, by limiting the number of fixtures on a long run or by using heavier gauge wire.

Pro-quality multi-tap landscape lighting transformers often have different output voltages on different taps. It’s not uncommon in a large transformer to see a couple of 12V taps, as well as a 13V, 14V, and 15V tap. These taps can help ensure that you’re getting the necessary voltage to the end of the line.

Timers vs photocells

Odds are, you don’t want to have to flip a switch every time you want your landscape lights to come on. Home automation setups are one solution, but that’s way above my knowledge level. The two most common automated controllers we use are timers and photocells.

Timers come in analog or digital. The analog ones look like the ones your parents used to have the lights come on when you were on vacation. The downside to these is that if you lose power, it can throw off your entire program. Digital timers often come with a battery backup, so when the power comes back, nothing has changed. Timers are best for people who want the lights to come on at dusk, but turn off when everyone usually goes to bed. When they come on needs manually adjusted as the seasons change.

Photocells are good for homeowners who want the lights to come on when it gets dark, and shut off when the sun comes back. The sensor can mount directly on the transformer if it’s out in the open. If the transformer is inside a building or under a deck, you can get a photocell on a longer wire lead that can be mounted remotely.

Bottom line: a landscape lighting transformer is the heart of your outdoor lighting system. It’s the most expensive individual component, which is why we recommend getting the best one that fits your budget, and sizing it to fit your current and future needs. If you’re not sure where to start with your landscape lighting, that’s just one of the many services we offer. Contact us today to learn more!

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