Voltage drop, cable sizing, driver sizing and wiring advice for 12V & 24V outdoor LED lighting
Calculate the voltage drop across your cable run and check if your cable size is adequate. Recommended maximum drop: 5% (ideally β€3% for LED fittings).
Size your garden lighting transformer or constant voltage driver with the correct safety margin. All garden LED fittings use constant voltage (CV) drivers β the driver maintains a fixed 12V or 24V output regardless of load.
Not sure whether to daisy-chain your fittings or run separate spurs? Enter your details for a wiring recommendation.
Australian wiring rules allow up to 5% voltage drop at the point of use. For 12V that's 0.6V. For 24V that's 1.2V.
Most LED garden fittings tolerate Β±10% input voltage but perform best within 3% drop (β€0.36V on 12V). Beyond 5%, expect dimming and colour shift at far-end fixtures.
| Voltage | 3% Max | 5% Max |
|---|---|---|
| 12V | 0.36V | 0.60V |
| 24V | 0.72V | 1.20V |
Your transformer or external driver maintains a fixed voltage (12V or 24V). Current varies depending on how many fittings are connected. All multi-fixture garden systems are CV. Fittings connect in parallel.
Some premium garden fittings contain an internal CC driver that converts the 12V/24V CV input into the precise fixed current (e.g. 350mA or 700mA) the LED chip needs. You never interact with this β it's invisible to the installer. The external system is always CV.
CC drivers are for specific LED packages β not for multi-light garden systems or LED strip. Always use CV for garden installations.
| Size | Ξ©/100m | Max current |
|---|---|---|
| 0.75mmΒ² | 2.33Ξ© | ~6A |
| 1.0mmΒ² | 1.75Ξ© | ~10A |
| 1.5mmΒ² | 1.17Ξ© | ~13A |
| 2.5mmΒ² | 0.70Ξ© | ~18A |
| 4.0mmΒ² | 0.44Ξ© | ~25A |
| 6.0mmΒ² | 0.29Ξ© | ~32A |
Based on copper conductor at 20Β°C. For outdoor buried cable, derate by ~10% for temperature.
A 1V drop on a 24V system is only 4.2% β manageable. The same 1V drop on a 12V system is 8.3% β well outside the LED fitting's tolerance. This is why 24V systems are far better for longer garden runs. The physics is identical but the percentage impact is halved.
Daisy-chaining runs one cable from fitting to fitting β simple but every fitting downstream suffers accumulated voltage drop. A home-run layout runs an individual spur from the driver to each fitting β higher cable cost but every fitting sees the same voltage. For runs over 15m or more than 4 fittings, home-run wins.
Many quality CV drivers β including the MeanWell HLG, ELG and LPF series β have a built-in trim potentiometer that lets you adjust output voltage by Β±10%. On a 12V driver you can dial up to ~13.2V to pre-compensate for cable drop, so the far-end fitting still sees ~12V. A simple and effective trick for long runs without upsizing cable.
Some garden fittings run directly on 240V mains β typically flood lights, wall lights and some larger path lights. These must be installed by a licensed electrician, use outdoor-rated IP65+ weatherproof fittings, and comply with AS/NZS 3000 and any local council requirements. Mains garden circuits should be protected by a residual current device (RCD).