Installing an inverter safely

The safe-install rules split at the inverter: DC on one side, 230V AC on the other. The DC side, battery, cables, fusing, mounting, you can generally do yourself with the correct cable, fusing and connections. Fixed 230V AC wiring, hardwired circuits and socket outlets fed by the inverter in a caravan, motorhome or boat, has to be done and certified by a registered electrician, to AS/NZS 3000 and AS/NZS 3001.2, and under AS/NZS 3001.2:2022 an inverter-fed circuit in a connectable installation needs RCD protection like any other 230V circuit. And in some cases, if you are the homeowner, you can do some of the electrical work yourself and then get it inspected by a registered electrical inspector.

The DC side is where most installs actually go wrong, and it's fully in your control. Mount the inverter close to the battery, short fat cables; give it airflow, because an inverter is also a heater; and use the cable size the current demands, not a random pick. A 2200W inverter flat out is ~180A at 12V, and the DC voltage drop calculator tells you what that needs in cable size over your run length. Torque the terminals properly: a loose high-current connection gets hot, and hot connections are where voltage is lost and fires start.

Fuse the positive cable, sized both to the cable and the inverter as you have to protect them both; the inverter is usually the most restrictive. Where it goes depends on more than one thing: close to the battery is common, but it's more practical to have your fuses and breakers in one place, close to where you'd notice a problem and could operate the isolation straight away, not scattered where you'd have to hunt for them. Fit a battery switch as the DC isolator, so the inverter can be fully disconnected for maintenance without pulling lugs.

The AC side has one idea to understand: an inverter is a 230V source, and 230V from an inverter is exactly as dangerous as 230V from the mains supply. Plugging one appliance into the inverter's own socket is use, not installation, and that's fine. The moment 230V is wired into the structure, a caravan's outlets, a boat's AC panel, a house circuit, it's fixed wiring: registered-electrician territory, certified to the standard, with RCD protection on the circuits. The RCD point is widely missed on inverter circuits, and a fault on an inverter-fed circuit can be as lethal as one on mains. The 2022 edition also requires low-voltage and extra-low-voltage systems to be physically separated: AC and DC breakers go in different enclosures with an air gap between the enclosures.

Two more things that separate a good install from an incident. Never let the inverter's output meet another 230V source, shore power or a generator, on the same circuit; two sources on one circuit is how equipment and people get hurt, and the answer is a transfer switch or an inverter-charger, never a double-ended lead. If any of this is news, get the electrician in before the install, not after the incident. The auto-electrician page has the components for a compliant install, and more is in our Installation & wiring FAQ.