| Decision | Record | Do not assume |
|---|---|---|
| Lighting job | Path guidance, accent target, step, or hardscape task | One fixture type solves every scene |
| Electrical load | Exact model, quantity, and manufacturer-specified W or VA | Fixture count is a load calculation |
| Transformer | Capacity, taps, controls, environment, and reserve | A larger wattage alone proves compatibility |
| Cable run | One-way length, load placement, topology, conductor, and tap | Distance alone chooses wire gauge |
| Commissioning | Staged operation, measurements, nighttime aim, and project record | Daytime placement is the final aim |
Begin with zones, not products
Sketch the areas you want to light: walking paths, steps, planting beds, trees, gathering spaces, and the route back to power. Each zone has a different job, so it may need a different fixture type and beam pattern.
A useful first plan records fixture positions, approximate cable paths, and which fixtures should share a run. That map matters more than choosing a finish early.
- Mark obstacles and crossings
- Keep future expansion in mind
- Separate ambient, path, and accent-lighting goals
Calculate load with reserve
Create a run schedule before selecting a transformer: record each exact fixture model, quantity, manufacturer-documented W or VA, operating-voltage range, location on the run, and evidence URL. If the selected manufacturer requires VA, do not substitute watts or infer a value.
Add the documented planning load, then apply a clearly stated reserve margin. The margin is planning headroom, not permission to ignore transformer limits, tap compatibility, individual-run constraints, controls, or voltage drop.
Our planner uses the values you enter and labels its capacity result as a screen. A product recommendation is eligible only when its exact documented load, voltage range, system identity, and relevant compatibility fields support the calculation; sharing an outdoor-lighting category is not enough.
- One row per exact model and run
- Evidence URL beside every electrical input
- Unknown load or voltage data stays a manual-review blocker
Treat wire selection as a circuit question
Distance alone cannot determine cable size. Current, voltage, load distribution, run topology, connection quality, temperature, and acceptable voltage drop all matter. A long run with lights distributed along it behaves differently from the same total load placed at its far end.
Use the planner's cable estimate for purchasing length, then validate conductor size and layout against fixture and transformer instructions and applicable code.
Commission the system deliberately
Before burial or final concealment, energize the completed run, confirm fixture operation, inspect connections, and measure voltage where the manufacturer recommends. Adjust aim after dark, when glare and dark spots are easy to see.
FAQ
How much transformer reserve should I plan?
A planning margin of 20% is a common starting point, but the transformer's instructions and control system requirements govern the final design.
Can cable length alone tell me the wire gauge?
No. Current, load placement, topology, voltage, allowable voltage drop, environment, and manufacturer instructions all affect conductor selection.
Sources and evidence
Links support factual statements; they do not turn manufacturer claims into independent measurements.
- Kichler — choosing a landscape transformer Accessed 2026-10-28
- Kichler — calculating project load size Accessed 2026-10-28