Understanding Voltage Drop in Low-Voltage Landscape Lighting Systems

Understanding Voltage Drop in Low-Voltage Landscape Lighting Systems

Low-voltage systems are standard for landscape lighting, but many homeowners don’t understand the underlying electrical issues. If you are planning a low-voltage landscape lighting system, you will need to consider certain properties of the electrical wiring or your system will fail. A key to planning a successful landscape lighting system is understanding voltage drop in low-voltage landscape lighting systems.

Why Voltage Drop Matters

The most basic goal of wiring in your landscape lighting system is simply to deliver electricity to all of your lights. Without the right amount of electricity, your lights won’t work. And if your lights don’t work, no amount of creativity or planning will save your landscape lighting design.

Getting enough electricity to each of your fixtures is not as simple as just sending out a wire that connects all of your lights back to a power source. The nature of electrical wiring is such that it acts as a resistor. It doesn’t send 100% of the electricity at the source all the way down the wire. So if you don’t plan your landscape lighting with that in mind, you will end up with some lights that are not receiving the electricity they need to shine with their full brightness. And what good is landscape lighting if the fixture don’t glow as you planned?

Understanding Voltage Drop [infographic]

The Difference Between Low-Voltage and Standard Voltage

Standard voltage for commercial and residential buildings in the United States is 120 volts. This is a great voltage for use in wiring buildings. It allows for reasonably sized conductors (in other word the wires) to conduct electricity without significant voltage drop.

All conductors are, to some extend, resistors. This means that the farther a current travels, the weaker it becomes. At 120v, less current, measured in amps, is required to provide the wattage needed for home lights and appliances. With a lower current, there is less voltage drop.

But when it comes to outdoor landscape lighting, 120v has some drawbacks. The largest drawback is that it is dangerous to work with. You wouldn’t want to come into contact with the wires in your house. You could risk a serious shock. In general, if you are working with home wiring you are probably an electrician, plus you have the power switched off. Otherwise, the average homeowner shouldn’t be interacting too much with their home wiring. The wiring in hidden in the walls of your home and you have little occasion to mess with it.

With landscape lighting, the wiring is much more exposed. It may be buried in a relatively shallow ditch in a garden. Wiring cal also run along decks, up trees, along the base of a wall, and other exposed areas. Landscape lighting is also more a DIY project for a lot of homeowners. So to keep everyone safe, landscape lighting manufacturers settled on 12 volts as a standard. Most landscape lighting requires relatively low wattage, so you don’t need the extra voltage anyway. And you are much less likely to injure yourself with 12v than with 120v.

What Causes Voltage Drop

Voltage drop is a result of the quality of your conductors. In general, nothing is a perfect conductor of electrical energy. For some special uses, scientists have developed highly conductive materials and wires that lose very little voltage. These are known as superconductors and they have many important uses.

But when it comes to consumer conductors used for transmitting electricity to power our devices, it is much more cost effective to use copper and other common wiring materials. These materials do a fine job of transmitting the electricity we need for all of our various appliances.

However, with these consumer grade conductors, there is some significant resistance. That resistance increases with smaller gauge wire and higher currents. At 120v and with standard gauge wire, the resistance is usually not an issue. But with 12v sending a stronger current, the resistance can become an issue if not properly planned for.

How to Avoid Voltage Drop

The key to planning a successful landscape lighting system is understanding voltage drop and how it affects your layout. No matter what you do, the voltage at the end of your wire will be lower than the voltage at the energy source. But you can plan your lighting layout in a way that will minimize voltage drop. This will ensure that all of the fixtures in your lighting design are receiving adequate energy to function at their full desired brightness.

The main issue in voltage drop is distance and the number of light fixtures. The more light fixtures on a single run of cable and the longer the cable, the greater the voltage drop. So the key to avoiding voltage drop is to limit those factors. Having fewer fixtures on a single run of cable will allow each fixture in a series to draw more current.

Some Ideas for Avoiding Voltage Drop

There are a few ways to design your electrical layout so that you don’t have too much distance or too many fixtures on one line.

  • Multiple Straight Runs. Instead of snaking a long cable around to reach all of your lights, use a few shorter lines that each include just a few lights and less total distance. You will need to make sure that your transformer is centrally located.
  • Loop Design. You can design your wire route so that it reaches each fixture and then returns to the transformer. This will give a more even voltage to each fixture. Just make sure that you match the polarity of your wires to the transformer.
  • T-Design. With a t-design, you run one cable out from your transformer to a central spot, then run a cable in two (or more) directions from there. You can use heavier gauge wire for the first run so there is less resistance, then switch to the smaller gauge for the runs with the lights on them.

By employing these designs or using a combination of these techniques, you can ensure that each fixture is getting the voltage it needs.

Calling in the Pros

Of course, while the 12v standard has made it safer and easier for homeowners to do it themselves, there is no replacement for the professionals. If you have any question about your lighting, you might consider calling in help. The friendly professionals at Night Vision Outdoor Lighting will work with you to come up with a plan that works.

One of our designer/installers will discuss all aspects of your project with you. We will listen to what you need, what you want, and what your budget allows for. Then we will work with you to come up with a plan that is aesthetically pleasing and electrically sound. We’ll make sure that you end up with lighting that looks great and works like a charm. And you’ll have no need to worry.

Are you ready to add some excellent outdoor lighting to your home? You’re definitely in the right place. Just browse around our website to see what we do. You can see some pictures of our recent projects here. Want to hear from customers just like you who loved our work? Our testimonials page is full of helpful reviews. And when you are ready, you can visit our contact page to set up a consultation to figure out what the best lighting solution will be for your unique needs.