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low voltage outdoor lightingLow voltage outdoor lighting is a great way to accent your home's appearance, enhance security, and increase the safety of those who walk around your property at night. It's a relatively simple process and is an easy one day project to add about a half dozen lights, do the wiring, and hang the transformer. The materials are available at your local home store, although I recommend that, for a truly professional look, you consider buying at least the transformer and lights from a landscape lighting dealer -- it will be more expensive (imagine that !), but the return, in terms of durability and serviceability, will be worth the added expense.

A little planning is called for, before you head out to buy stuff. Landscape lighting should be situated to accent architectural features, specimen plantings or hardscapes, and provide secure access to areas such as paths,walkways, and steps. Don't light the front of your home so that it looks like the exercise yard at the county jail, but don't be chintzy so that it appears you ran out of materials. Lay out the approximate sites for the lights, add about 3' at the ends for fine-tuning the positioning (you'll do it, believe me), and compute the total footage so you can buy the correct amount of wire.

Low voltage outdoor lighting(click thumbnails to view gallery)

Low voltage transformerUplight for treeLight cable wall penetrationCable running in driveway expansion joint

Some general guidelines for the most visible elements of the lighting system:

  • path lights should be 10-12' apart and not directly across from each other -- the dreaded "runway lights" effect
  • area lights are for things like boulder walls, mass planting areas, or play areas
  • spots are for sculptures, water features, or trellised plantings
  • recessed lights are for walkway or deck steps
  • uplights are for trees, large plantings, or those things with a significant vertical element; keep in mind that large trees will need more than one light to adequately illuminate the branches.
  • think about the future and how the growth of plants will affect, and require, repositioning of the lights
  • as for lamp selection, most on-line catalogs are not able to accurately represent their products; I recommend that you visit a local dealer to handle the lights and visualize their place in your landscape.

Let's get started with materials:

  • transformer -- this baby changes your home's 120 volt alternating current (ac) power to 12 volt direct current (dc) so that it is not only easier to do the installation, but is much safer, given the drop or "step down" in voltage and current. Most transformers have a max load rating of 300 watts; they have either an analog or digital timer and/or can be outfitted with a photocell to turn the lights on at dusk and off in the morning. You will have to plug the transformer into a 110v outlet; if you select an outdoor transformer, you need to consider ease of access and vandalism/theft concerns and you will have to plug it into a GFCI protected outlet.
  • lights -- there are a bazillion sizes and types of lights; most come with ground stakes for ease of installation; you can also get telescoping stakes if you have to get the lights off the ground (e.g. if there are small plants, in front of your light, which interfere with the line of sight to your desired lighting subject.) Use the guidelines in the intro to determine what kind, and how many, you need. The lamps for the lights generally come in ranges from 4 to 50 watts--most folks use lamps in the 10, 20, or 30 watt range. No matter the size transformer you use, try not to use more than 80% of the transformer's capacity -- that will give you room for some future expansion (you know you'll do it) and you won't have dim lights at the end of the line from line resistance. If, for example, you have a 300 watt transformer, you can install a total of about 240 watts (300 watts x 80% = 240 watts); you could have 24 x 10 watt lamps, 8 x 30 watt lamps, 10 x 20 watt lamps + 4 x 10 watt lamps, and so on.
  • wiring -- once you've laid out your lighting, determined the number and size of the lamps and the transformer size, and calculated the necessary cable length runs (+ 10%, not that you'd ever make a mistake), use the following guidelines to determine wire size:
  1. 150 watt transformer: 100' +/- of 16/2 wire
  2. 200 watt transformer: 125' +/- of 14/2 wire
  3. 300 watt transformer: 150' +/- of 12/2 wire ( don't ask -- wire size numbers decrease as physical size increases)
  4. Hint -- now that you've done all this calculation work, just get a 300 watt transformer and 12/2 wire; that will allow you to install about 8 x 30 watt lamps, with some room for later additions. From experience, I can tell you that will do a very nice job for an average front yard.

Now the fun part begins:

  • Figure out where you will hang the transformer -- you need to be within the cord length of an outlet; a 300 watt transformer is fairly heavy, so choose the appropriate hangers for an interior wall or outdoor stake. An indoor transformer should be sited close to an exterior wall, so you can drill a hole for the leads to go outside. Wait until you have laid out your leads so you only have to drill the hole once, then you can seal the penetration with a silicone caulk. My preference is to hang the box close to a garage door so you don't end up running a bunch of wire just to get to the outside, where you now have to run a bunch more to get to the lights.
  • Run the wire to your light sites, adding about 3' for future positioning requirements. Follow the transformer wiring instructions; as a rough guideline, don't put more than 4 or 5 lights on a single circuit, so that bulb dimming is minimized ( we covered this before, remember?)
  • Tentatively position your lights (you'll want to refine their location after dark), set them loosely in the ground, hook up the cabling and run the wires back to the transformer.
  • Set the timer (you can play with it to activate your lights and check their operation) or implement the photocell (which you can also play with by duct-taping over the "eye".)
  • You don't need to bury the wiring; you can lay it on the ground and cover it with mulch or gravel or leaves or a planted ground cover. For turf areas, using a garden spade, knife the wire about 3" deep into the sod and call it a day. Remember, it's low voltage -- if you should accidentally cut the wire, you won't get shocked, you'll just have to repair it. For hard surfaces, like a driveway, the easiest way is to run the wire in the expansion joint. If you don't have this handy little groove, you have to saw-cut the driveway (not much fun) or tunnel under the driveway (even less fun).
  • Safety: before this, or any project where you dig into the soil, get your utilities marked; nothing says angry neighbor like a severed CATV line. You likely would never feel a cut 12v dc wire, but a cut 440v ac line or natural gas line will put you into low earth orbit! Probably not a good feeling.

There you have it; good luck and wait for the waves of admiration from family and friends.

(All photos by Bill Volk)

  • Roseli A. Bakar

    Good info mate :)

  • Bill Volk


  • j

    How about solar?

  • Melbourne Electrician

    Great source of information and tips. Thanks

  • 4 Comments / 1 Pages

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