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 ≤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 — 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 ±10% input voltage but perform best within 3% drop (≤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 — it's invisible to the installer. The external system is always CV.
CC drivers are for specific LED packages — not for multi-light garden systems or LED strip. Always use CV for garden installations.
| Size | Ω/100m | Max current |
|---|---|---|
| 0.75mm² | 2.33Ω | ~6A |
| 1.0mm² | 1.75Ω | ~10A |
| 1.5mm² | 1.17Ω | ~13A |
| 2.5mm² | 0.70Ω | ~18A |
| 4.0mm² | 0.44Ω | ~25A |
| 6.0mm² | 0.29Ω | ~32A |
Based on copper conductor at 20°C. For outdoor buried cable, derate by ~10% for temperature.
A 1V drop on a 24V system is only 4.2% — manageable. The same 1V drop on a 12V system is 8.3% — 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 — simple but every fitting downstream suffers accumulated voltage drop. A home-run layout runs an individual spur from the driver to each fitting — 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 — including the MeanWell HLG, ELG and LPF series — have a built-in trim potentiometer that lets you adjust output voltage by ±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 — 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).
Low voltage garden lighting transforms outdoor spaces but requires careful design to get right. The two most common problems are lights that dim at the far end of the run (voltage drop) and drivers that overheat or trip (undersizing). This guide covers everything you need to design a reliable garden lighting system.
The choice between 12V and 24V comes down to run length and total wattage. Both voltages are safe to handle and widely available, but they behave very differently over distance.
| System | Best For | Max Practical Run | Notes |
|---|---|---|---|
| 12V | Small gardens, short runs | ~5m at 1.5mm² | Widest product range, most common |
| 24V | Larger gardens, longer runs | ~15m at 2.5mm² | Half the current = quarter the voltage drop |
| 48V | Very long commercial runs | 40m+ | Less common for residential |
At the same wattage, a 24V system carries half the current of a 12V system. Since voltage drop increases with current, this means 24V systems have dramatically less voltage drop over the same cable length — making 24V the professional's choice for any run over 5 metres.
Voltage drop is the reduction in voltage along the cable from driver to light. For LED garden lights, even small drops matter — a 10% drop on a 12V system means lights receive only 10.8V instead of 12V, which can cause noticeable dimming and reduce LED lifespan.
The key levers to reduce voltage drop are: use larger cable, shorten the run, switch to 24V, or split into multiple shorter runs each fed from the driver.
| Cable Size | 12V Max Run (10W/light × 4 lights) | 24V Max Run | Suitable For |
|---|---|---|---|
| 1.0 mm² | ~3m | ~6m | Very short connection leads |
| 1.5 mm² | ~5m | ~10m | Standard short runs |
| 2.5 mm² | ~8m | ~16m | Most garden installations |
| 4 mm² | ~13m | ~26m | Longer runs, higher loads |
| 6 mm² | ~20m | ~40m | Large garden, commercial |
These figures assume a maximum 10% voltage drop. For critical installations or colour-sensitive lighting, design for 5% maximum drop.
Daisy-chain connects lights one after another along a single cable. It is simple and uses less cable, but voltage drop accumulates at each fitting — the last light in the chain always receives less voltage than the first, causing uneven brightness.
Home-run wiring runs a dedicated cable from the driver or a junction box to each individual light. Every light receives the same voltage, brightness is consistent, and a fault on one cable does not affect the others. Home-run is the preferred method for quality garden lighting installations.
A common compromise is a star or radial layout — a heavier main cable runs from the driver to a central junction box in the garden, then shorter home-run cables feed each light from the junction. This minimises total cable while keeping voltage consistent.
Add up the total wattage of all lights, then multiply by 1.2 for the 20% safety buffer. For example:
For outdoor drivers, choose IP67 rating minimum. MeanWell LPV, HLG and ELG series are industry standards — avoid cheap unbranded drivers for permanent outdoor installations as they can fail in heat or moisture.
| IP Rating | Protection | Use For |
|---|---|---|
| IP44 | Splash proof | Covered outdoor areas, verandahs |
| IP54 | Dust + splash proof | General outdoor use |
| IP65 | Dust-tight + water jets | Path lights, spotlights, exposed outdoor |
| IP67 | Temporary immersion (30 min, 1m) | Ground recessed lights, near water features |
| IP68 | Continuous submersion | Pond lights, underwater features |
In Australia, garden lighting installations must comply with AS/NZS 3000 (Wiring Rules). Key requirements include: