Landscape Lighting

Low-voltage landscape lighting fails in exactly one way: the fixtures at the far end are dimmer than the ones at the start. It is always voltage drop, and it is always discovered after the cable is buried.

Three numbers, worked out together

Fixture count from run length and spacing. Transformer rating from total load — never run one above 80% of its nameplate, because a transformer at full rating runs hot and heat is what kills them. Cable gauge from voltage drop over the run.

Get any one of the three wrong and the system underperforms in a way that looks like a faulty fixture.

Current is halved, and that is correct

With fixtures spread evenly along a run, the full load current only flows in the first section of cable. By the far end almost nothing is left. Calculating as though the whole load ran the whole distance doubles the apparent drop and sells you twice the copper.

The window is narrow

12 V LED fixtures want 10.5–15 V. Below that they visibly dim and some flicker; above it they fail early. Ten percent drop is the practical ceiling, and it is tighter than the 3% branch-circuit convention would suggest is necessary — because there is no headroom to spare at 12 volts.

Two fixes that cost nothing

Feed from the middle rather than one end. That halves the effective distance and roughly quarters the drop, for the price of a different trench route.

Leave headroom on the transformer. Landscape lighting always grows — one more fixture at the new tree, two more along the path. Sizing to exactly today's load means buying a second transformer next spring.

Multi-tap is compensation, not a substitute

Transformers with 13, 14 and 15 V terminals exist to compensate a long run. They work. But raising the voltage at the source to fix undersized cable also raises it at the near fixtures, which then run hot.

Choosing the fixture type for the job

Voltage drop decides whether the system works. Fixture choice decides whether it looks like anything.

Path lights cast a pool downward from a low head, usually 18–24 in tall. Spaced 8–12 ft apart — closer produces a runway, which is the most common mistake in a front garden. They light the path, not the garden.

Spotlights are directional and used for uplighting a tree, a wall or a feature. Beam angle matters more here than anywhere else outdoors.

Well lights are recessed into the ground, invisible by day, and used for uplighting where a visible fixture would be in the way. They need drainage under them and they collect leaves.

Wash and flood fixtures have a wide beam for lighting a facade or a hedge evenly.

Step and deck lights are low output — often 10–30 lumens — mounted into risers or posts. This is a safety fitting and brightness is a hindrance: anything bright at ankle level is glare in the eyes of someone coming down.

Hardscape or under-cap lights tuck under a wall coping or bench edge and wash the surface below.

A garden lit entirely with one type looks like a car park. Two or three types doing different jobs is what reads as designed.

Beam angle outdoors

Indoors, beam angle affects spacing. Outdoors, it decides whether a fixture does its job at all, because the distances are much greater.

The rule that follows from the geometry: the further the throw, the narrower the beam. A wide flood aimed at the top of a 30 ft tree spills most of its light into the sky and the neighbour's garden and puts very little on the tree.

Connections are the real failure point

Voltage drop is what the design gets wrong. Connections are what fails two winters later, and they cause more callbacks than everything else combined.

Use proper waterproof connectors. Gel-filled or silicone-filled direct-burial connectors rated for the purpose. Twist-on wire nuts wrapped in tape are not waterproof, and a buried joint is where water goes.

Do not bury a joint you can avoid burying. Keep connections above ground where possible, inside a fixture body or a junction box, and record where the buried ones are.

Leave a service loop — a foot of slack cable — at every fixture. Ground moves, roots grow, and a taut cable eventually pulls a connection apart.

Bury the cable properly. Typically 6 in deep, in conduit under anything that will ever be dug, and away from where a spade goes in spring.

Use direct-burial rated cable, not indoor flex. The difference is the jacket, and the jacket is the whole point.

Do not over-light, and do not light the neighbours

The commonest fault in a finished garden is too much light, and it has three causes: fixtures bought on brightness, no dimming, and no consideration of where the light goes after it leaves the fixture.

Aim down, or shield. A fixture aimed upward at a tree should have a shroud or a glare guard so the source is not visible from the house next door or from a bedroom window.

Warm colour, 2200–2700K. Warm light scatters far less in the atmosphere, attracts far fewer insects, and disturbs wildlife less than cool light. It also simply looks better on planting and stone.

Low output. Outdoor eyes are dark-adapted. A 200 lumen fixture that would be trivial indoors is substantial in a dark garden, and most path lights need 30–100 lumens rather than the several hundred often fitted.

Put it on a timer or an astronomical clock, and turn it off at a sensible hour. A garden lit all night serves nobody, costs money, and is the thing neighbours remember.