Can I run a kettle and a microwave at once?

Only if the inverter, the cable and the bank were sized for that coincidence. Most liveaboards pick one heating appliance and treat the other as a shore-power luxury.

Do I need a true sine inverter?

For anything with a switch-mode supply, a motor or a delicate charger, yes. Modified sine is how you own a warm fridge controller and a buzzing laptop brick.

12-volt or 24-volt for a 2,000-watt inverter?

24-volt (or 48 on bigger boats) once the continuous load is in the kilowatt class. The cable on 12 volts becomes a heating element.

Onboard power · 11 min read · Updated 2026-08-26

Inverter sizing for Australian liveaboards

Size an inverter for the one appliance you will not give up, then for the minutes it runs. A 3,000-watt sticker is not a meal plan.

Houseboats moored on the Coomera River, Gold Coast

Liveaboard Australian boats — the Coomera houseboat, the Broadwater motor cruiser, the yacht that spends winter in the Whitsundays — eventually want a kettle, a laptop and a charger that does not hum. An inverter is the 240-volt story. It is also a battery story. Size one without the other and you will own a quiet evening and a loud morning.

Write the appliance list

Be cruel. A kettle is 2,000 watts for three minutes. A microwave is similar. A hair dryer is a joke you will try once. A CPAP is a quiet, all-night load. A laptop is nothing. A coffee machine with a thermoblock is a kettle in costume.

Pick the largest single load you will not give up, then decide whether anything else will run at the same time. That coincidence is the inverter rating. A 2,000-watt true sine unit covers a kettle or a microwave on most boats. A 3,000-watt unit is how couples stop negotiating.

Continuous versus peak

Motors and compressors want a surge. Cheap inverters lie about surge. Buy a marine or at least a reputable true-sine unit whose continuous rating matches the appliance, and whose surge is published, not implied. Victron-class inverter/chargers are common on Australian liveaboards because the charger half is the shore-power story. See Victron systems.

The bank has to agree

A 2,000-watt kettle on 12 volts is about 180 amps plus losses. That is a lithium conversation, or a very large AGM and a short evening. Read lithium versus AGM. If the boat already has a watermaker, add that pump to the same study — how much water a cruiser needs is the other half of liveaboard maths.

Voltage and cable

Once you are in the kilowatt class, 24-volt house systems stop being a luxury. If you stay on 12 volts, the cable and the fuses must be enormous and short. Voltage drop is how toasters get slow and inverters alarm.

Installation

Ventilate. Fuse both sides as the manual says. Keep AC output on its own distribution so a kitchen fault does not look like a charger fault. Do not invent an earth that the boat did not have. 240 volts on a vessel is still 240 volts.

If you do not live aboard, you may want a 300- to 500-watt inverter for laptops and camera chargers, and nothing else. That honesty is cheaper than a silent house bank.

Frequently asked questions

Can I run a kettle and a microwave at once?: Only if the inverter, the cable and the bank were sized for that coincidence. Most liveaboards pick one heating appliance and treat the other as a shore-power luxury.
Do I need a true sine inverter?: For anything with a switch-mode supply, a motor or a delicate charger, yes. Modified sine is how you own a warm fridge controller and a buzzing laptop brick.
12-volt or 24-volt for a 2,000-watt inverter?: 24-volt (or 48 on bigger boats) once the continuous load is in the kilowatt class. The cable on 12 volts becomes a heating element.