What Is a Campervan Inverter? How to Choose the Right Size for Running Appliances [2026]

You arrive at the RV park, ready for dinner. You put frozen rice in the microwave, press start, and the power inside the van cuts out — a surprisingly common problem on campervan trips. The cause is almost always one of two things: the inverter doesn’t have enough capacity, or the appliance isn’t compatible with the inverter’s waveform. This article digs into what an inverter actually does and, more importantly, how to choose one that won’t let you down. The real story isn’t the wattage printed on the appliance’s label — it’s “starting wattage,” and that’s the core of this guide.

The short version: if you want to run 1,000W-class appliances like a microwave or hair dryer, the rule of thumb is a pure sine wave inverter rated at around 1,500W or more. But if you don’t understand where that number comes from, you’ll run into the same failure depending on which appliances you combine. Let’s go through the reasoning in order.

Without an inverter, you can’t run household appliances in the van

The electricity stored in a campervan’s sub-battery is 12V DC (24V in some vehicles). Household appliances like microwaves and hair dryers, on the other hand, need 100–120V AC. The type of current and the voltage are both different, so plugging an appliance straight into the battery won’t do anything. The inverter is what bridges the two — it converts 12V DC into AC and sends it out through the outlets inside the van.

Solar “adds power in,” an inverter “turns it into power you can use”

It’s easy to lump inverters in with solar panels, but the two jobs are completely separate. Solar panels and engine charging are on the “generating and storing” side — they put electricity into the sub-battery. An inverter is on the “converting” side — it turns the electricity you’ve already stored into a form your appliances can use. No matter how much you generate, the microwave won’t run if the inverter’s capacity falls short. And no matter how big the inverter is, nothing happens if the battery is empty. You need both working together before you can actually “run appliances inside the van.”

For the generating side — how to calculate how many Wh a day your solar panel can produce — see the Campervan Solar Panel Complete Guide. For the full picture of the electrical system, including the sub-battery, engine charging, and shore power, start with the Campervan Electricity & Power Complete Guide — it’ll make this article’s place in the bigger picture clearer. From here on, this article sticks to just one side of the equation: choosing the right inverter.

Pure sine wave or modified sine wave — which one do you need?

Inverter output waveforms fall into two broad categories: “pure sine wave” and “modified sine wave.” Modified sine wave models cost less, but the range of appliances they can safely run is much narrower — worth understanding before you buy.

Pure sine wave: the same waveform as a household outlet

A pure sine wave is the same smooth waveform that comes out of a household wall outlet. It’s said to run everything reliably, from laptop and camera chargers to motor-driven appliances and even sensitive medical devices. If it works on your home outlet, you can generally assume it’ll work here too.

Modified sine wave: some appliances run, some don’t

A modified sine wave approximates a sine wave with a stepped, stair-like shape. Simple heat-producing devices like incandescent bulbs tend to run fine, but motor-driven appliances — compressor-type fridges, fans, vacuum cleaners — and devices with delicate control circuits are reported to be at risk of noise, humming, overheating, malfunction, or outright failure. “It turned on, but something’s not right” is the kind of problem this waveform tends to cause.

The bottom line is simple: if you can’t pin down in advance exactly which appliances you’ll use on the road, go with pure sine wave. For rentals, too, whether the vehicle’s built-in inverter is pure sine wave or not determines what you can safely bring along.

Sources: explanation of inverter waveform differences / what a sine wave is / pure sine wave vs. modified sine wave (all checked August 24, 2026).

Where to check on the spec sheet

Check the label. If it says “sine wave” or “pure sine wave,” you can take that at face value. If it says “modified sine wave,” “quasi sine wave,” or “square wave,” it’s the stepped waveform. If there’s no mention of waveform at all, don’t guess — ask the rental company or seller directly. A rental vehicle’s spec sheet will often list waveform and output together, something like “pure sine wave inverter, 1,500W” — look for that one line.

Where capacity choices go wrong: “starting wattage”

The “XX watts” printed on an appliance’s label is its steady-state power draw while running. But many appliances briefly demand much more than that the instant they switch on — when a motor starts spinning, or when a fridge’s compressor begins compressing refrigerant. That brief spike is called “starting wattage” (or surge power), and it’s the single biggest trap in choosing an inverter.

How big can starting wattage get?

As a rough guide, some appliances have a starting wattage of roughly 1.1–2x their steady-state draw, while others jump to 2.1x or more. In some cases the instantaneous spike can reach several times, even more than 10 times, the steady-state value. For example, a vacuum cleaner drawing around 350W steady-state may need 850W or more to start, and a small electric kettle drawing around 900W steady-state may need 950W or more. The math of “it’s a 500W inverter, so a 350W vacuum has plenty of headroom” falls apart right at the moment of startup.

Source: guide to appliance power draw and starting wattage (checked August 24, 2026). Starting wattage varies significantly even between models of the same appliance type, so check your specific device’s manual or nameplate.

A 4-step approach to choosing capacity

1. List the appliances you want to use on your trip (microwave, hair dryer, electric blanket, and so on)
2. Add up the steady-state power draw of everything you’ll run at the same time
3. Identify which of those simultaneously-running appliances has the highest starting wattage
4. Choose an inverter whose rated output exceeds whichever is higher — the combined steady-state total, or the single largest starting wattage — with a 20–30% margin

Step 3 is the key one. If you size your inverter only by the combined steady-state total, you can end up with the protection circuit tripping and everything shutting off the moment a fridge compressor kicks in. If you want to run 1,000W-class appliances like a microwave or hair dryer, a pure sine wave inverter rated at around 1,500W or more is the figure that keeps coming up as the common benchmark across multiple campervan-related guides (as of August 24, 2026).

Running the numbers: a family of four on an autumn overnight trip

Let’s try a real example. A couple with two kids, one night in Hokkaido in October. They want to use a microwave (about 1,300W), two electric blankets (about 50W each), and a laptop (about 60W).

Running everything at once adds up to roughly 1,460W steady-state. With a 1,500W inverter, there’s no real margin left once you account for the microwave’s starting surge. So they adjust their routine instead: turn the electric blankets off for the few minutes the microwave is running. That drops the simultaneous load to about 1,360W at most — comfortably workable on a 1,500W-class unit. Bumping up capacity isn’t the only answer; designing which appliances run together is a legitimate way to manage capacity too.

That said, going oversized “just to be safe” isn’t automatically the right call either. A bigger inverter draws more standby power on its own, and it needs thicker wiring to handle the higher current. Size to what your appliances actually need, add a 20–30% margin, and that’s enough.

How much power do microwaves and hair dryers actually draw?

Here’s a rough rundown of the power draw for appliances people tend to want inside the van. These are all steady-state figures and vary by model — check the label or manual for what you’re actually bringing.

Appliance	Typical power draw	Notes for in-van use
Microwave	~1,300W	The “500W” on the dial is heating output, not input power draw — actual draw is higher
Hair dryer	600–1,200W	High settings push right up against capacity limits; start on low
Hot plate / griddle	~1,300W	Long run times drain the battery fast
Rice cooker	350–1,200W	Draw spikes during the cooking phase; a small model for fewer people is more realistic
Vacuum cleaner	1,000–1,100W	A classic case where starting wattage far exceeds steady-state draw
Coffee maker	450–650W	Only draws power while brewing; relatively easy to manage
Refrigerator (small–medium)	150–500W	Watch for compressor startup surge; said to be a poor fit for modified sine wave
Laptop	50–120W	A sensitive device — best run on pure sine wave
Electric fan	50–60W	Motor-driven, so it’s sensitive to waveform

Source: appliance power consumption list (checked August 24, 2026). These figures represent a typical range — actual draw varies by model.

Looking at the table, a pattern emerges: appliances that generate heat (microwave, hair dryer, hot plate) tend to run over 1,000W, while everything else stays in the low hundreds or under. Even with a 1,500W-class inverter, running a 1,300W microwave and a hair dryer at the same time is out of the question. Using big appliances one at a time is the basic rule inside the van.

Having enough inverter capacity is one thing — having enough battery is another

There’s another balance that’s easy to overlook: the sub-battery. Run a 1,500W appliance off a 12V battery, and the math works out to over 120A of current. A single 100Ah sub-battery can’t sustain that for even an hour, in theory. In practice, microwave heating only takes a few minutes, so the battery won’t drain instantly — but “the inverter’s output is enough” and “the battery has enough charge left” are two different questions, and keeping that distinction in mind will save you from a scramble on the road. For how many Wh you actually have to work with, see the Campervan Electricity & Power Complete Guide.

Renting? Here’s what to check before you book

With a rental, you’re not choosing an inverter — you’re checking what’s already installed in the vehicle. Here are the three things worth confirming before you book:

• Output wattage: Does it exceed the starting wattage of what you want to run? If you’re planning on a microwave, a 1,500W-class unit is usually the dividing line
• Waveform: Pure sine wave or modified sine wave? If you’re bringing motor-driven or precision devices, look for a pure sine wave vehicle
• Balance with sub-battery capacity: Even a high-output inverter won’t run big appliances for long if the battery behind it is small

These three details often aren’t listed on the spec sheet, so if you don’t see them, ask the rental company directly before booking. If you’re set on using a microwave, you can also confirm whether the vehicle’s electrical design was built with that in mind. Equipment varies by vehicle even within the same company, so don’t assume “it worked on the van I rented last time” will hold true this time.

Staying somewhere with shore power means you don’t have to rely on the inverter

Most campervans have a shore power inlet, and at many RV parks or powered campsites, plugging in a cable feeds outside 100V straight to the outlets inside the van. In that state, you can use appliances the same way you would at home, without worrying about the inverter or your battery level (within the limits of the site’s own circuit breaker).

So if you definitely want to use a hair dryer or hot plate, the simplest fix is to build a stop with shore power into your route. Even a vehicle with a smaller built-in inverter can be covered by choosing where you stay. How shore power interacts with battery charging and 100V supply differs by vehicle, so it’s worth asking about at pickup so you’re not guessing later.

One more thing worth noting for a Hokkaido winter trip: heating is usually handled by a fuel-burning FF heater in most campervans, not the inverter. What you’d want electrically is limited to things like an electric blanket (around 50W) or lighting. Thinking of it as “heating runs on fuel, big cooking appliances run on shore power or the inverter” makes planning a winter itinerary much easier.

FAQ

Q: Can I charge a smartphone on a modified sine wave inverter?

Most USB chargers are said to work, but depending on how the device’s AC adapter reacts, you can run into overheating or charging problems. For something as simple as a smartphone, it’s more sensible to skip the inverter entirely and use the vehicle’s USB port or a cigarette-lighter charger — less conversion loss, too. Sensitive devices like laptop or camera chargers are recommended to run on pure sine wave.

Q: Is a bigger inverter always better?

Not necessarily. A larger inverter draws more standby power, quietly draining the battery even when nothing is plugged in. Price and wiring requirements go up too. Sizing to the starting wattage of the appliances you actually want to use, plus a 20–30% margin, tends to be the choice you’re happiest with for the money.

Q: Can I run a microwave and a hair dryer at the same time?

Combined, that’s roughly 2,500W — normally more than a vehicle inverter can handle. Use them one at a time. Even when you’re plugged into shore power at an RV park, the site’s circuit breaker (often a 15A / roughly 1,500W circuit) can trip if you exceed it, so avoiding simultaneous use of big appliances is a good rule of thumb even on shore power.

Q: Should I bring a portable power station instead of using the vehicle’s inverter?

A portable power station combines a battery and an inverter into one self-contained unit, so it’s convenient because it doesn’t touch the vehicle’s own electrical system. It’s a solid backup option if the vehicle’s built-in inverter output is small and you want to run a few-hundred-watt appliance. Large capacity models capable of handling 1,000W-class loads like a microwave, though, come with matching weight and price. For a rental, the sensible order is to first check whether the vehicle’s own equipment is enough, then bring a power station only to cover the gap.

Q: Can I run appliances off the inverter while driving?

While driving, engine charging is feeding the sub-battery, so many vehicles can handle a small load like an electric blanket while underway. That said, what’s allowed and the upper limit both depend on the vehicle’s electrical design, and for a rental, the company’s own guidance takes priority. Confirming “what’s OK to use while driving” at pickup will save you from second-guessing yourself for the rest of the trip.

Choosing an inverter really comes down to one thing: knowing the starting wattage of the appliances you want to use. Before your next booking, write down three appliances you’d like to bring, and compare the biggest starting wattage among them against the vehicle spec’s output rating. Do that, and you’re done with trips where the power cuts out right at dinnertime.