Quick answer
Choose a pure sine wave inverter with a continuous rating above the total wattage of everything you’ll run at once, and a surge rating that covers start-up loads such as fridges, compressors and power tools. Mount it close to the battery with short, heavy cables and a fuse or circuit breaker near the battery, because inverters draw very high current at 12V. Plug appliances straight into the inverter’s own outlets. Connecting an inverter into a caravan’s or vehicle’s fixed 240V wiring is licensed electrical work.
Is this a DIY job?
- Difficulty: Medium for a small inverter with its own outlets; Pro for large inverters; licensed electrician only for any fixed 240V wiring
- Time: 1 to 3 hours for a stand-alone install
- Tools: heavy cable crimper, cable cutter, socket set, multimeter, drill
- Skills: high-current DC wiring
Step by step
- List what you’ll run. Find the wattage on each appliance’s label. Add up everything you’ll use at the same time.
- Choose the continuous rating. Pick an inverter rated comfortably above that total. Running an inverter at its limit for long periods makes it hot and less efficient.
- Check the surge rating. Motors and compressors (fridges, blenders, power tools) can draw several times their running power for a moment at start-up. The inverter’s surge rating must cover that.
- Choose pure sine wave. Pure sine inverters produce power like a household outlet, so laptops, chargers, motors and sensitive electronics run properly. Modified sine inverters are cheaper, but some appliances run hot, noisy or not at all.
- Check your battery can supply it. At 12V, the DC current is roughly the AC watts ÷ 12, plus inverter losses. A 1,000 W load draws more than 80 A from the battery. Make sure the battery, and its charging, can support that. (see How much solar do I need for my caravan?)
- Choose the location. Close enough to the battery to keep the DC cables short, but not inside the battery box or right beside the battery: some makers specify a minimum gap, so check the manual. It should be dry, well ventilated, protected from damage and away from battery gases.
- Disconnect the battery negative first before you fit any fuse or cable. Reconnect it last, once everything else is done.
- Fit the DC fuse and isolator. A fuse or circuit breaker rated for the inverter (from the maker’s instructions) goes as close to the battery positive as practical. An isolator switch makes it easy to turn off.
- Run short, heavy DC cables. Use the cable size the inverter maker specifies, and keep the run as short as possible. (see What size cable do I need for my 12V accessory?)
- Connect the chassis earth if the inverter maker requires it, using the specified cable.
- Use the inverter’s own outlets. Plug appliances directly into the inverter, or use an appliance lead rated for the load.
- Leave fixed 240V wiring to a licensed electrician. Connecting an inverter to a caravan’s power points, changeover switch or shore power needs correct earthing, RCD protection (an RCBO, which also gives overcurrent protection) and compliance with AS/NZS 3001.
- Test and check heat. Run your normal loads and check cables, lugs and the inverter don’t get hot.
Specs table
Approximate DC current at 12V (allowing for about 10% inverter loss)
| AC load | Approx. battery current |
|---|---|
| 100 W | about 9 A |
| 300 W | about 28 A |
| 500 W | about 46 A |
| 1,000 W | about 93 A |
| 2,000 W | about 185 A |
Real current varies with the inverter’s efficiency and the battery voltage. Check the maker’s figures.
Pure sine vs modified sine
| Pure sine wave | Modified sine wave | |
|---|---|---|
| Output | Smooth, like household power | Stepped approximation |
| Laptops, chargers, electronics | Run normally | May run hot, buzz or fail |
| Motors and compressors | Run normally | May run hot or noisy |
| Cost | Higher | Lower |
What you’ll need
- pure sine wave inverter
- ANL fuse holder or circuit breaker (rated per the inverter maker)
- battery isolator switch
- heavy duty single core auto cable (size per the inverter maker)
- cable lugs and adhesive heat shrink
- battery monitor (to watch consumption)
When to call an auto electrician
- Any inverter above a few hundred watts, or any install with long DC cable runs.
- You want the inverter connected to a caravan’s or vehicle’s 240V power points, changeover switch or shore power. That’s licensed electrical work and must comply with AS/NZS 3001.
- The inverter shuts down under load, alarms for low voltage, or cables get hot.
- You also need a DC-DC charger, solar and a larger battery to support the inverter.
Need an auto electrician? Find local auto electricians and mobile services in your city.
Related questions
Q: What size inverter do I need for a coffee machine or microwave? A: These are high-wattage appliances. Check the label: you’ll need an inverter rated above that figure, a battery bank that can supply the very high DC current, and heavy cabling. For many setups, it’s a big step up.
Q: Can I plug my inverter into my caravan’s power inlet? A: Don’t do this yourself. Back-feeding power into a caravan’s 240V wiring can be dangerous. A licensed electrician can install a proper changeover arrangement with RCD protection.
Q: Why does my inverter beep and shut off? A: Usually low battery voltage under load, cables too thin or long, or the load is beyond the inverter’s rating. Check battery charge and cable size first.
Q: Is it safe to leave an inverter on? A: Inverters draw some power even with nothing plugged in. Switch it off when not in use to save your battery.
Sources
- REDARC, “Guide to AC wiring when installing a pure sine wave inverter in a vehicle” – fixed AC wiring by a licensed electrician; RCBO and changeover switch requirements; AS/NZS 3001. https://www.redarcelectronics.com/eu/resources/redvision-wiring-guides/guide-to-ac-wiring-when-installing-a-redarc-pure-sine-wave-inverter-in-a-vehicle (checked October 2026)
- WorkSafe ACT, “Electrical incident” – fatal incident involving non-compliant 240V wiring in a trailer; 240V installations in caravans and transportable structures to be done by a licensed electrician and certified to AS/NZS 3001. https://www.worksafe.act.gov.au/health-and-safety-portal/safety-alerts/electrical-incident (checked October 2026)
- Solar4RVs, “Understanding cable size types: mm, mm², B&S, AWG” – typical cable sizes for inverters. https://www.solar4rvs.com.au/buying/buyer-guides/understanding-cable-size-types-mm-mm2-b_s-awg/ (checked October 2026)
- REDARC, “RS Series 12V & 24V Pure Sine Wave Inverters instruction manual” – DC fuse on the positive as close as practical to the battery; short DC cables sized to the maker’s table; ventilation clearance; don’t mount in a battery compartment or close to a battery; chassis earth; no-load current draw; permanent AC installs by a licensed electrician. https://cdn.intelligencebank.com/au/share/yE9N/zJpl/rDD2O/original/RS+Series+Pure+Sine+Inverters+Instruction+Manual (checked October 2026)