Before you dig
Ten minutes on paper, and you only order cable once
Nobody gets this exactly right first time, including us. But getting the load and the longest run roughly right is the difference between one delivery and three.
What size transformer
Put in how many of each you are thinking of. The headroom figure is the one that matters — a transformer run flat out gets hot and dies early.
Once the answer passes 150 watts, two transformers on two runs beat one big one: the drop halves, the cable can drop a gauge and half the garden stays lit when something goes wrong.
Six steps, in pencil
Squared paper, one square to a metre. It does not need to be pretty, it needs the distances on it.
Everything is measured from there, and it is the one thing people forget to put on the sketch.
Not where you want a lantern — where you want the light to land. The fitting usually ends up a metre to one side of it.
Follow the edge of beds and paths. Cable that goes round things survives digging; cable that cuts across them does not.
A tape lies to you on curves. String laid along the route and then measured straight is honest.
That is the transformer size. The calculator above does it, but the arithmetic is not hard.
How far apart
Distances we have arrived at by getting them wrong first. They suit a Norfolk garden with mature planting; an open new-build takes everything a half-metre wider.
| Where | Spacing | The bit people miss |
|---|---|---|
| Straight path | 2.5 to 3 m apart, alternating sides | Closer than 2 m and it reads as runway lighting |
| Curved path | 2 m apart on the outside of the curve only | The inside of a bend needs nothing; the light carries across |
| Steps | One per two risers, or a deck light per tread | Low and to the side, never facing up the stairs |
| Border or bed | One spotlight per plant worth looking at | Two metres back, angled up at about 30 degrees |
| Tree | 1.5 to 2 m from the trunk, two lights opposite | One light flattens it; two give the canopy some depth |
| Gate or entrance | A pair, level with each other | The one place symmetry actually matters |
Three layouts that work
The simplest garden. Transformer in the middle of the path, cable going both ways. Halves the voltage drop for nothing.
Path one way, borders the other. Each spur carries its own load, so a spade through one leaves the other lit.
For a big garden. Both ends of the loop go back to the transformer, so every fitting is fed from two directions at once.
Send us the sketch
Photograph the squared paper and attach it to the enquiry. We will come back with the cable length, the transformer and anything on the plan that will annoy you in three years.