Key takeaways
- A 12V inverter turns your battery into usable 240V power, but where you mount it and how you wire it decides whether it runs safely or becomes a fire risk.
- Mount the inverter in a dry, well-ventilated spot as close to the battery as practical, with the isolation switch within easy reach.
- Cable is sized by current, not watts. A 2000W inverter can pull 170A to 200A at 12V, so it needs heavy cable and a short run.
- Fit a DC fuse or circuit breaker within roughly 150mm of the battery to protect the cable from a dead short.
- The 240V side, including earthing and an RCD on the output, is regulated work in Australia and usually needs a licensed electrician.
Anyone who has spent a long weekend off-grid knows the value of having a bit of mains power at camp. A 12V inverter makes it possible, converting the 12V DC stored in your battery into the 240V AC power your laptop, coffee machine, or CPAP machine needs.
But where should you actually install one? And what size cable does a 12V inverter need?
Getting the mounting position, cable size and fusing right is important for safe, reliable operation. Get them wrong, and you could end up with voltage drop, overheated wiring or a damaged system. This guide covers where to install a 12V inverter in a caravan or 4WD, what cable it needs, and when to leave the installation to a licensed professional.
Deye 16kW Hybrid Inverter Single Phase 290A Max Charge
What a 12V Inverter Actually Does
A 12V inverter draws current from your house battery and steps it up to 240V so you can run normal appliances away from mains power. For a caravan or 4WD, choose a pure sine wave model. It produces clean power for laptops, medical devices and anything with a motor, whereas cheaper modified sine wave units may buzz, run hot or refuse to work with modern gear. Size the inverter by its continuous rating and your real loads, not the surge figure on the box.
Where to Install a 12V Inverter in a Caravan or 4WD
The best mounting position balances three things: keeping the inverter cool, keeping the DC run short, and keeping the controls within reach.
Pick a Dry, Well-Ventilated Spot
Inverters are efficient but not perfect. A 2000W unit running near capacity can shed 200W or more as heat, so it needs airflow. Mount it where the cooling fan has clear space around it, per the clearances in the manual, and keep it out of sealed lockers, away from water, and well clear of gas cylinders, fuel and the fridge exhaust. A vented cupboard or a well-ventilated bay under a seat works well in a caravan. In a 4WD, the rear cargo area or a drawer system is common.
Mount It Close to the Battery
Every extra metre of cable adds resistance, which means voltage drop and heat. The closer the inverter sits to the battery bank, the shorter and cheaper the heavy DC cable can be and the better it performs under load. Keep each run as short as practical, ideally under two metres.
Keep It Accessible for Isolation
You need to switch the inverter off quickly and reach a battery isolation switch in a hurry, so do not bury the unit behind other gear. Being able to read the display, reset the unit and cut the DC feed matters both for everyday use and in an emergency. Isolation accessibility is a safety feature, not a convenience.
Deye 48V 6KW Hybrid Solar Inverter MPPT Charger Regulator Low Voltage
What Cable Size a 12V Inverter Needs
This is where most home installations go wrong. The temptation is to size the cable by wattage, but the number that matters is current.
Work It Out By Current, Not Watts
Current draw rises as voltage falls, so a 12V system pulls more amps. As a rough guide, divide the inverter output by the battery voltage and add a margin for about 85% efficiency. A 2000W inverter, such as the VoltX 12V 2KW Pure Sine Wave Inverter, draws roughly 170A to 200A at 12V at full load. A 3000W inverter, like the VoltX 12V 3KW Pure Sine Wave Inverter, can pull 250A or more. Those are serious currents that demand serious cable.
| Inverter size | Approx. continuous current at 12V | Typical cable, short run |
|---|---|---|
| 1000W | ~90A | 6 B&S to 4 B&S |
| 2000W | ~180A | 2 B&S to 00 B&S |
| 3000W | ~270A | 0 B&S to 4/0 |
Indicative only for short runs. Always confirm against the inverter manual and a voltage drop chart.
Keep Voltage Drop Under About 3%
Long or thin cable wastes power and can shut the inverter down on low voltage. A good target is to keep voltage drop under about 3%, which is roughly 0.36V on a 12V system. If your run has to be longer, step up a cable size rather than pushing your luck. Size the negative cable the same as the positive, finish every termination with properly crimped lugs and heat shrink, and use marine-grade or automotive cable rated for the current. Loose or undersized connections commonly cause heat and failure.
Fusing and Circuit Protection
A fuse is not optional. A fully charged 12V 100Ah deep cycle battery, including the Outbax VoltX 12V 100Ah LiFePO4 Battery, can deliver thousands of amps into a dead short, easily enough to melt cable and start a fire before you notice.
Fit a Fuse Close to the Battery
Install a DC fuse or circuit breaker within roughly 150mm to 300mm of the battery positive terminal, as close as you practically can. Its job is to protect the cable, so a fuse close to the battery catches a short anywhere along the run almost instantly.
Match the Rating to the Cable and the Load
The fuse should be rated above the inverter’s maximum continuous draw but below the cable’s safe capacity, which for a 2000W inverter often lands around 200A to 250A. High-current DC fuses such as ANL, MEGA, or Class T are designed for this duty, and the inverter manual will usually state a recommended size.
Earthing, RCD Protection, and the Legal Line
The 240V side of an inverter install is where many people get out of their depth, and where Australian rules are strict.
Earth Bonding and Why It Matters
For safety devices to work, the inverter output usually needs correct earth bonding, a defined link between neutral and earth. Many inverters ship with a floating output that can stop protective devices from operating as intended, and some offer a switchable neutral-to-earth bond for exactly this reason. Getting it right is essential.
Fit an RCD on the Output
Any 240V outlets fed by the inverter should sit behind a 30mA RCD on the output, so an earth fault trips the supply fast. Crucially, an RCD only works if there is a proper neutral to earth reference, which loops back to correct earth bonding. This is one reason the output side is treated as skilled work.
Know When You Need a Licensed Electrician
In Australia, fixed 240V wiring in a caravan or camper is regulated under standards such as AS/NZS 3000, and it is illegal to carry out fixed 240V electrical work yourself. You can usually handle the 12V DC side, the battery, fuse and cable up to the inverter. A licensed electrician should install or certify the 240V outlets, earthing, and RCD. At Outbax, we would rather a customer pay a sparky for the 240V side than gamble on the part of the job that can hurt someone.
VoltX 12V 3KW Pure Sine Wave Inverter
12V Inverter or a Portable Inverter Generator?
A hardwired 12V inverter is brilliant for light and occasional 240V loads. It is silent, needs no fuel, and draws on power you already store. But it has a hard limit: your battery.
When a 12V Inverter Is the Right Call
For charging laptops, running a few lights, a fan, or a small coffee machine, an inverter paired with a healthy lithium battery is ideal. Because current draw is high, lithium (LiFePO4) handles the load far better than older lead-acid batteries and recovers faster.
When a Generator Makes More Sense
Run the maths on a big load and the picture changes. A 2000W draw pulls around 170A, which flattens a single 100Ah battery in well under an hour. For air conditioning, induction cooking, power tools, or long runs of high demand, a portable inverter generator is the practical answer because it makes continuous 240V without draining your bank.
This is where the Outbax range earns its keep. The Gentrax Inverter Generator 4.2kW Max 3.5kW Rated Pure Sine Wave is a popular camping and RV choice, while the 3.5 kW Silent Inverter Generator suits campers who value quiet. For convenience, the Gentrax 3.5kVA Inverter Generator Remote Electric Start fires up at the push of a button, and for bigger jobs, the Gentrax 7.7kW Max 7.0kW Inverter Generator Home Backup covers heavier loads and home backup duty.
To size a generator, add up the running watts you plan to use at once and leave headroom for surge. Many tourers end up with both, an inverter for quiet, low-draw jobs and a generator for the heavy lifting.
VoltX 12V 2KW Pure Sine Wave Inverter + FREE VoltX Inverter LCD Display
Getting Your 12V Inverter Install Right
A safe install comes down to a short list: mount the inverter somewhere dry and well-ventilated, keep it close to the battery, size the cable by current, fit a fuse right at the battery, and leave the 240V side to a licensed electrician. Do those five things and a 12V inverter will give you quiet, reliable mains power wherever you park.
If your loads are heavier, or you would rather not lean on your battery at all, a portable inverter generator is the simpler path. Browse the Outbax range of inverter generators and caravan batteries to match the right setup to the way you travel.
