How to choose the right inverter for your camper van

An inverter is a device that transforms DC (Direct Current) from your battery bank into AC (Alternating Current), the same type of power you have at home. In Europe this means 230V at 50Hz, in North America 120V at 60Hz. Not every camper van needs an inverter. If you only charge phones, run LED lights and use a 12V compressor fridge, you can get by entirely on 12V DC. But as soon as you want to use household devices like a laptop charger, an electric kettle, a coffee machine, a hair dryer or power tools, you need AC power. The inverter sits between your battery bank and a 230V outlet or distribution panel. It draws DC current from the batteries and outputs AC power. Keep in mind that this conversion is not 100% efficient. A typical inverter loses 10-15% of the energy as heat during conversion. That means a device drawing 100W from the AC side actually consumes about 115W from your batteries. This efficiency loss is important when sizing your battery bank and solar panels. Always factor in inverter losses when calculating your total daily power consumption.

Inverters come in two main types: pure sine wave (PSW) and modified sine wave (MSW). The difference lies in the shape of the AC waveform they produce. A pure sine wave inverter produces a smooth, continuous wave identical to what the electricity grid delivers. All devices work correctly on a pure sine wave. This includes sensitive electronics like laptops, medical devices (CPAP machines), microwave ovens, variable-speed motors and audio equipment. A modified sine wave inverter produces a stepped, blocky approximation of a sine wave. It is cheaper, but many devices do not run well on it. Motors run hotter and noisier, laptop chargers may overheat, LED dimmers buzz, and some devices refuse to start altogether. Clocks and timers may run inaccurately. For a camper van, a pure sine wave inverter is almost always the right choice. The price difference has shrunk considerably in recent years, and the compatibility with all devices gives you peace of mind. A good-quality 1000W PSW inverter costs between 150 and 300 euros. Only consider a modified sine wave inverter if you exclusively power simple resistive loads like incandescent bulbs or basic heaters, and you are on a very tight budget.

Every inverter has two power ratings: continuous (or rated) power and surge (or peak) power. Continuous power is what the inverter can deliver indefinitely. Surge power is what it can handle for a few seconds when a device starts up. To size your inverter, list all the AC devices you might run at the same time. Add up their wattage. That total is your minimum continuous power requirement. Then check if any of those devices have high startup currents: compressors, power tools and devices with electric motors often draw 2 to 5 times their rated wattage for the first second. Example: you want to run a laptop charger (65W), a phone charger (20W) and a blender (300W) simultaneously. That is 385W continuous. The blender motor may surge to 900W on startup. So you need an inverter with at least 400W continuous and 900W surge, a 600W unit with 1200W surge would give you comfortable headroom. A common rule of thumb is to size your inverter at 125-150% of your maximum expected simultaneous load. This gives you margin for efficiency losses and prevents the inverter from constantly running at full capacity, which shortens its lifespan. Also consider the DC current draw. A 2000W inverter on a 12V system pulls up to 180A from the battery. That requires very heavy cables (50 mm² or more) and a suitable fuse. Think about whether you truly need that much power.

Proper installation of your inverter is critical for safety and performance. The inverter should be mounted as close to the battery bank as possible to minimise cable length and voltage drop on the DC side. Keep cables under 1.5 metres if you can. Use appropriately sized DC cables. For a 1000W inverter on 12V, expect around 90-100A of DC current. That requires at least 25 mm² cable for short runs and 35 mm² for anything over 1 metre. Always install a fuse or circuit breaker on the positive cable, rated for the cable's maximum capacity, not the inverter's power rating. Ventilation is essential. Inverters generate heat, especially under load. Mount the unit in a well-ventilated space, not inside a sealed cabinet. Many inverters have built-in fans, but they still need airflow around them. Keep at least 10 cm of clearance on all sides. On the AC (output) side, use standard household wiring practices. Install an RCD (Residual Current Device, also called GFCI in North America) to protect against electric shock. Wire the AC output to a small consumer unit or distribution board with individual MCBs (Miniature Circuit Breakers) for each circuit. Finally, install a remote on/off switch if your inverter supports it. Inverters draw a small amount of standby power (5-20W) even when nothing is connected. Turning it off when not in use saves your battery capacity.