What Size Inverter Do I Need for My Campervan?

An inverter turns the 12V DC power in your leisure battery into the 230V AC your household appliances expect. Get one that's too small and it trips the moment you flick on the coffee machine. Get one that's too large and you're wasting money, space and standby power. This guide walks you through exactly how to size your campervan inverter, from understanding surge watts to picking the right cable gauge and choosing between the most popular models on the market.

1. What is an inverter and why do you need one?

Your campervan's electrical system runs on 12V (or 24V) direct current. That's fine for LED lights, USB chargers and a compressor fridge, but the moment you want to plug in a laptop charger, a coffee machine, a hairdryer or a blender, you need 230V alternating current (or 120V AC in North America). An inverter bridges that gap: it takes the DC power stored in your leisure battery and converts it into the AC power that comes out of a normal household socket.

Without an inverter, you're limited to devices that run natively on 12V or USB. That rules out most kitchen appliances, power tools, medical devices like CPAP machines, and many entertainment devices. For anyone doing more than weekend camping with a cool box, an inverter is a core part of the electrical system.

The key specification on any inverter is its continuous wattage rating — the sustained power it can deliver without overheating or shutting down. A "1000W inverter" can continuously supply 1000W of AC power. Most inverters also list a peak (surge) wattage, typically 1.5-2x the continuous rating, which they can sustain for a few seconds to handle the inrush current when a motor or compressor kicks on.

2. Pure sine wave vs modified sine wave

Inverters come in two families, and the difference matters more than most buyers realise.

Pure sine wave (PSW) inverters produce a smooth, sinusoidal AC waveform — identical to what comes out of a wall socket at home. Every appliance works perfectly: variable-speed motors run quietly, digital clocks keep time, laptop chargers stay cool, and audio equipment produces clean sound with no buzz or hum.

Modified sine wave (MSW) inverters approximate the sine wave with a stepped, blocky waveform. They cost 30-50% less, but the rough waveform causes problems. Motors in blenders and fans may overheat and run louder. Dimmable lights flicker. Some modern switch-mode power supplies in laptop chargers won't work at all or produce excessive heat. CPAP machines and other medical devices often carry explicit warnings against modified sine wave power.

3. How to size your inverter

Sizing an inverter comes down to two numbers: the continuous watts you need and the peak (surge) watts your appliances demand on startup.

Step 1 — List every 230V appliance

Go through every device you plan to plug into the inverter. Ignore anything that runs on 12V or USB — those bypass the inverter entirely. For each appliance, note its rated wattage (printed on the label or in the manual) and whether it has a motor or compressor (which means a startup surge).

Step 2 — Add up the continuous watts

Add the wattage of every appliance you might run at the same time. You probably won't run the coffee machine while blow-drying your hair, so be realistic — but do add the laptop charger that's always plugged in and the phone charger sitting on the counter.

Step 3 — Check the surge requirement

Any appliance with a motor, compressor or heating element draws a large inrush current for 0.5-3 seconds at startup. This surge is typically 2-3x the running wattage for motors and up to 5-7x for large compressors. Your inverter's peak rating must cover the highest single surge while also carrying the other appliances that are already running.

Step 4 — Add a 20% safety margin

Running an inverter at 100% continuous load generates excessive heat, shortens its lifespan and leaves no headroom. Multiply your continuous total by 1.2 to build in a comfortable margin.

Worked example: you want to run a laptop charger (65W), a phone charger (20W) and a coffee machine (1200W) at the same time. The continuous total is 1285W. Multiplied by 1.2, that's 1542W. The coffee machine surges to about 1800W on startup. A 2000W pure sine wave inverter covers both requirements with room to spare.

4. Common appliance power ratings

Use this table as a quick reference when adding up your loads. Surge watts are approximate — check your specific model's label for exact figures.

5. Sizing table by use case

If you want a quick answer without adding up individual appliances, find your row in this table.

The most popular choice for campervans in 2026 is a 2000W pure sine wave inverter. It handles a coffee machine, a microwave, a laptop and a phone charger without breaking a sweat, and it's compact enough to fit under a bench seat. If your only 230V loads are a laptop and a phone charger, a compact 300-500W unit saves weight and standby power.

6. Battery impact — how inverter size affects drain

An inverter doesn't create energy — it converts it from your battery, with losses. A typical pure sine wave inverter is 85-90% efficient. That means for every 100W of AC power delivered to your appliance, the inverter actually pulls 111-118W from the 12V battery.

To calculate how many amps your inverter draws from the battery bank:

Worked example: running a 1200W coffee machine for 10 minutes on a 12V system at 88% efficiency:

That's 113.6A for the duration — but since you only run it for 10 minutes (1/6 of an hour), the actual energy consumed is 113.6 / 6 = 18.9 Ah. On a 200Ah lithium battery (160Ah usable at 80% DoD), that single coffee costs about 12% of your usable capacity.

* 700W microwave uses ~1100W input power. All figures at 88% inverter efficiency.

The takeaway: high-wattage appliances through an inverter drain your battery fast. A battery autonomy calculator is essential to understand how many hours of inverter-powered use your bank can actually sustain. Every watt through the inverter costs roughly 10% more from the battery than the appliance's rating suggests.

7. Cable sizing for inverters

Undersized cables between the battery and inverter are a fire hazard and a performance killer. At 12V, a 2000W inverter draws nearly 190A — that's more current than a car starter motor. The cables must be short (ideally under 1.5 metres) and thick enough to carry the load without significant voltage drop.

Use this table to pick the minimum cable cross-section for runs up to 1.5 metres (each way). For longer runs, go one size up.

Always install an appropriately rated fuse on the positive cable, as close to the battery terminal as possible. The fuse should be rated slightly above the inverter's maximum draw — for a 2000W inverter at 12V, a 200-250A ANL or MEGA fuse is standard. Without this fuse, a cable short could melt wiring or start a fire before any other protection kicks in.

8. Popular models compared

This table compares well-regarded inverters available in Europe and North America in 2026. Prices are approximate street prices at time of writing.

Victron is the gold standard in the campervan world — excellent build quality, remote monitoring via Bluetooth (VictronConnect app), and rock-solid protection circuitry. They cost roughly double the Chinese brands, but many professional van builders spec nothing else. The MultiPlus line doubles as a battery charger when connected to shore power, making it a true inverter/charger combo.

Renogy offers strong mid-range value with good warranties and customer support. EDECOA and GIANDEL are budget-friendly options popular on Amazon — they deliver good performance for the price but may lack features like remote on/off switching or detailed Bluetooth monitoring. EPEver is a solid entry-level choice with surprisingly clean sine wave output for the price.

Whichever brand you choose, look for these protective features: over-voltage protection, under-voltage protection (shuts off before draining the battery too low), over-temperature protection, short-circuit protection, and ideally a remote on/off switch so you can mount the inverter near the battery but control it from the living area.

9. Common mistakes to avoid

• Confusing microwave output watts with input watts. A "700W microwave" draws 1000-1200W from the inverter. Always check the input power rating on the appliance label.
• Using the inverter for everything. Every watt that passes through the inverter loses 10-15% to conversion heat. If a 12V-native version of an appliance exists (USB chargers, 12V compressor fridges, 12V fans), use it instead and skip the inverter entirely.
• Cable runs that are too thin or too long. At high currents, undersized cables cause dangerous voltage drop and heat build-up. Keep runs under 1.5m and use the cable gauge table above.
• No fuse between battery and inverter. This is the highest-current circuit in your van. A short without a fuse will melt the cable in seconds. An ANL or MEGA fuse is mandatory.
• Leaving the inverter on 24/7. Standby draw of 0.5-2A doesn't sound like much, but over a week off-grid it can consume 80-340 Wh — that's 7-28 Ah from a 12V battery, enough to shorten your autonomy by half a day.
• Buying way too much inverter. A 3000W inverter has higher standby consumption, heavier cables, a bigger fuse, and takes up more space — all for capacity you may never use. Size for what you'll actually run, plus 20% margin.
• Ignoring surge requirements. A 1500W inverter might handle 1200W continuous all day, but if the coffee machine surges to 1800W on startup, it'll trip. Check the peak rating, not just the continuous.