What Size Inverter Do You Need for a Campervan?

Step 1 — add up what runs at the same time

Only count 240V appliances, and only the ones on simultaneously. A 2000W kettle plus an 1800W induction hob used together means a 3800W draw — but if you never run them together, size for the larger single load.

Induction hobs and kettles are the usual drivers. Laptops and TVs barely register.

Step 2 — apply the surge margin

Size the inverter at ~1.2× your peak simultaneous watts — motors and induction can surge above their rating on startup. 2000W of kettle means a 2400W+ inverter. And always pure sine: modified sine inverters are cheaper but can damage electronics and run motors hot.

Step 3 — the DC side is the dangerous side

At 12V the current is brutal: a 2000W inverter pulls ~170A continuously, and 3000W wants 250A+ — starter-motor territory. The DC feed needs 50–95mm² cable, an ANL or Class T fuse within 300mm of the battery, and a run kept under 1.5m.

This is also why 3000W at 12V is the practical ceiling — above that, a 24V bank halves the current and the cable size.

Do you even need one?

If everything runs on 12V or USB-C — fridge, lights, fans, laptops, Starlink (DC-modded) — an inverter is dead weight that idles power away. The calculator tells you when no AC loads are active.