Walk it first.
Pace - The walk
One pace is about 2.5 ft. Door to driveway, plus the branch paths.
Count - What gets lit
Trees, the facade, the steps, the wall cap, the pond.
Find - The outlet
The transformer needs a GFCI outlet outdoors. Pace from there to the first light.
Decide - The spacing
6–8 ft on a walk. Wider reads as a runway with dark gaps.
Step 02
How much to buy.
Nothing is sent anywhere. The math runs in your browser.
fixtures in total
watts drawn
transformer, at 80% load
more 3 W path lights fit
How the transformer number was picked
Add up the watts of every light on the run and keep the total under 80% of the rating. That last 20% is not capacity you are wasting — it is the margin that keeps the far end of the run bright, and it is where next spring's two lights by the shed go.
| Transformer | Path 3 W | Spot 5 W | Deck · hardscape 2.5 W | In-ground 12 W |
|---|---|---|---|---|
| 100 W | 26 | 16 | 32 | 6 |
| 200 W | 53 | 32 | 64 | 13 |
| 300 W | 80 | 48 | 96 | 20 |
| 600 W | 160 | 96 | 192 | 40 |
Counts use 80% of rated load with one fixture type on the run. A mixed run: add the watts of every light and stay under 80%. Wire gauge and run length change the answer; the wire guide covers both.
Step 03
Then you keep it running.
You have a count and a transformer size. Here is the part neither number tells you: when one of those lights fails, what do you actually have to buy?
an LED or a driver
the fixture, sealed shut
A ratio of 32. Not a repair cost — the cost of a design decision made before the light went in the ground.
One light fails. That is all it takes.
Two failures in five years: $310. Six: $930. It scales with how long you keep the yard.
Prices, stated so you can argue with them: $160 for a sealed fixture replaced whole, $5 for a replacement bulb. Published 2026 U.S. service pricing puts fixture replacement at $75–250 and bulb or socket replacement at $20–75. We have not measured how often fixtures fail and we are not going to pretend we have — the arithmetic above needs only one failure to hold.
A trip charge of $75–150 applies before anyone touches a part — and it applies to both rows equally, so it is not in the difference. That is the whole point: the level does not save you the trip. It decides what you carry in your hand when you get there.
Four levels, readable off any spec sheet
In reliability engineering the smallest thing you can swap in the field is the field-replaceable unit, and how fine it is drives what ownership costs. On a buried 12 V system it reads as four levels. You can place any brand on this scale from its own published specs, without taking anything apart.
| Level | What comes apart in the ground | What a failure costs you |
|---|---|---|
| D0 | Nothing. The fixture is one sealed unit. | A new fixture, every time |
| D1 | The light source comes out. | A bulb |
| D2 | Source, plus lens and gasket. | A bulb, or the part that let water in |
| D3 | Source, lens, gasket, plus stem, stake, connector and wire run. | Whichever piece actually failed |
HIBOITEC's replaceable-bulb lines sit at D1 and above. The bulb is a stock G4 or MR16 — the same socket as an under-cabinet or track light. Nothing on the job depends on us still being here in five years.
Connections and wire runs fail whether or not the fixture opens. On a 24-fixture, five-year model a D0 system and a D3 system get dug up about the same number of times — roughly 4.8 — because those failures have nothing to do with the light body. A finer replacement unit changes what you buy when you get there. It does not change how often you go.
Five years on die-cast aluminum, ten years on stainless, one year on bulbs. Coastal installs are included on all three — salt air is the usual exclusion in this category and we do not take it. Residential and commercial, same terms. Send the order number, the product name and one photo; a replacement ships from our U.S. warehouse in 1–2 business days, and for most claims we do not ask for the failed part back.
The arithmetic above is what happens after that. Which is exactly why the level matters: the warranty covers the part, and the level decides how big the part is.
Method — The D0–D3 scale applies the field-replaceable-unit concept from hardware reliability engineering to buried outdoor lighting. Part prices are stated assumptions, written out above rather than buried in a footnote. Cost ranges are U.S. published 2026 service pricing. Failure ordering is from professional installer documentation. All figures describe patterns, not precise outcomes.
You have the count. Now the parts.
Kits cover the common runs. Everything else is sold as singles on the same 12 V system.
