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How to Choose a Campervan Power Inverter for a DIY Campervan Electrical System

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If you’re planning on living in a van full time or even for a few weeks at a time, you might want to think about buying and installing an inverter.

Most campervan conversions include at least a small battery bank for charging 12v DC appliances and devices. 

But what about household appliances like charging laptops or running a TV? These need AC power so an inverter is an essential bit of kit.

This post will help you understand the basics of 12v power inverters so you can decide if you need one, what size it should be and other features to look for when buying.

We’ve recommended our top picks of 12v power inverters and included an installation guide at the end of the post too.

Avoid any confusion: Campervan Converters v Inverters – What’s the Difference?

Build your own camper quick start guide

12v Campervan Power Inverters | Our Top Picks

BESTEK Pure Sine Wave Power Inverter
  • 2 outlet plugs & 2 USBs
  • Protection against overheating, under and over voltage charging
  • Surge upto 700w
Renogy 700W 12V Pure Sine Wave Inverter
  • 2 outlet plugs
  • 700w continuous power & surge upto1400w
  • Overload protection for both DC input and AC output
BESTEK Pure Sine Wave Power Inverter
  • 2 outlet plugs & 2 USBs
  • 8 protection mechanisms
  • Surge upto 2400w
Renogy Power inverter
  • 2000w continuous power & surge upto 4000w
  • Overload protection for both DC input and AC output
  • LED indicators
Renogy Power inverter
  • 3000w continuous power & surge upto 6000w
  • Overload protection for both DC input and AC output
  • Quiet

What does an Inverter do in an RV?

In the most simple terms, an inverter changes DC power to AC power. But why would you need to?

AC power cannot be stored but DC power can. So 12v camper leisure batteries store DC power. 

You can wire your DC appliances to the battery and they’ll run happily. Things like LED lights, a 12v fridge, USB sockets and ventilation fans.

Appliances normally plugged into a household power outlet need an AC power source. 

So appliances like microwaves, laptop chargers, coffee makers or TVs, won’t run directly from the battery bank.

Instead, stored DC power must be converted to AC first and the inverter steps into do the job.

A diagram showing how a campervan power inverter works

Some RVs already have an inverter installed. But if your camper isn’t one of them, the in-built inverter has failed or you’re building a camper conversion, you can buy a separate inverter.

Why do I Need an Inverter in my RV?

The short answer is, you don’t.

If you can avoid running any AC appliances when off-grid, you don’t need an inverter.

With a shore power electric hook up, you can still run AC appliances when on a campground though.

Battery banks have a finite amount of power and whatever you use needs to be replaced, either from a camper solar setup or charging from the camper’s alternator when the engine is running. 

Solar panels on the roof of an RV

Avoiding powerful AC appliances where possible when not hooked up will help keep you off grid for longer and may save the need for a large battery bank.

All that said, if you still want to run even a small number of AC appliances on batteries only, you need an inverter.

Need more advice and support on a specific part of your campervan electrics? Join our new Facebook Group to connect with a growing community of like minded van builders.

How Does an Inverter Work?

DC power travels in one direction, seemingly a straight line.

AC power oscillates, changing direction between positive and negative voltages.

Basically an inverter consists of a series of switches, diodes or transformers.

As the DC current enters the inverter, these diodes open and close in rapid fire, either 50 or 60 times a second, depending on what frequency the supply provides.

This turns the straight line, single direction DC voltage into the characteristic wave of AC, amplifying its voltage value from 12v to either 110v or 240v, as per the manufacturers’s specification.

Different Types of Inverters

There are 3 different types of inverters:

  • Square Wave Inverter
  • Modified Sine Wave Inverter
  • Pure Sine Wave Inverter

What is a Square Wave Inverter?

As the name suggests, square wave inverters create a “square” wave. 

The inverter creates a “wave” that flips between positive and negative voltages instantly rather than more gradually. 

It pauses at the AC voltage level before flipping to the opposite polarity.

The component parts are simple, so square inverters are low cost.

This waveform is far removed from that of the mains supply, which is a pure sine wave.

Typically, square wave inverters are ok for running lights and mechanical fans. Sensitive electronics can be irreparably damaged if connected to one of these though.

The applications for square wave inverters is so limited, there’s very few, if any models available on the market today.

What is a Modified Sine Wave Inverter?

A modified sine wave inverter produces a stepped wave.

Rather than instantly flipping between extreme voltages, it produces a smoother waveform, though still a little clunky.

Following the general shape of a pure sine wave form, the voltage increases in increments with tiny pauses in between until it reaches the AC voltage level. 

Modified sine wave

The power inverter then reduces the voltage in similar incremental steps until it reaches the opposite polarity. 

With component parts more complex than a square wave model, modified sine wave inverters are more expensive but widely available.

A modified sine wave inverter can run simple appliances that don’t have sensitive electronics. 

Water pumps, camera battery and many laptop chargers will probably run just fine but other appliances like LED TVs or digital clocks won’t work.

What is a Pure Sine Wave Inverter?

A pure sine wave inverter most closely matches the power from a mains supply.

The voltages it produces increase and decrease in a smooth transition from positive to negative. 

The waveform is smooth, giving a clean consistent supply of energy.

Pure sine wave

This inverter will run all your electrical appliances and campervan gadgets

Though a pure sine wave inverter is more expensive than a modified sine wave, it won’t damage your sensitive electronics.

This is why we recommend pure sine wave over modified sine wave inverters.

What Size Inverter Do You Need?

Power inverters are sized in watts.

If you read any of the campervan conversion forums, you’ll likely see posts and conflicting opinions on what size inverter you need in a camper.

In theory, the inverter needs to be powerful enough to run the AC components connected to it at any given time. 

We recommend a rating of about 25% higher than the expected maximum load you intend to put on the system.

So let’s say you have a 240w slow cooker, a 200w blender and a 300w TV. 

The camper’s electrical system needs a much larger inverter to run them all at the same time than if you limit yourself to only using one at a time.

So why not just go for the largest inverter so you have the flexibility to run them all at the same time?

You can but remember, you can only take out of the batteries what you put in. 

Using inherently power hungry AC appliances needs a lot of battery juice and the solar panels or engine’s alternator need to recharge them so you don’t end up with flat batteries.

To help you figure out what size you need, we’re created an inverter calculator. It will also help you assess what size solar system you need to power it too.

What Size Battery Do You Need?

Campervan batteries should be sized to cope with your overall electrical demands.

To figure out the size needed, you need to take into account all expected load – both AC and DC appliances.

But converting DC to AC isn’t an efficient process so any AC calculations need to factor this in.

Use our battery bank calculator to help figure this out – it already takes inefficiencies into account so you don’t need to worry.

Battery Life Calculator

Many power inverters include in-built auto cut off features so they stop running if the battery bank falls to below a certain level. 

It’s a great feature to help protect the battery bank from over discharging and so help prolong their life.

If you have AC appliances you’ll only ever use when on a campground, like a washing machine or air conditioning, keep these on the main supply circuit and not the inverter. 

This will help keep the size of the battery bank needed down. 

What to Look for When Buying an Inverter

There’s a lot of inverters available on the market. 

Even once you’ve calculated the size needed, there’s other aspects of the component’s specification important to look at before making your final decision.

Continuous Power or Running Power

This is usually the labelled rating of the inverter. 

A 1000w inverter can provide continuous power of 1000w meaning it can supply this amount of power for as long as there’s a sufficient DC supply.

Peak or Surge Power Rating

Inverters can provide a greater surge of power in short bursts. This is especially useful for appliances that demand a power surge on start up, like a compressor fridge.

They take a large power surge to get going, before quickly dropping back to their running level.

Inverters often have a peak rating greater than the continuous power rating. 

Check your appliance specifications for any surge demand. 

Input Voltage

This indicates the voltage of the battery bank need to supply the inverter.

Most RV and campervan electrical systems have a 12v battery bank. Some have 24v and even fewer have 48v. Buy an inverter to match your battery bank voltage.

Output Voltage

Some manufacturers display the output voltage as a range. 

Buy an inverter the same output voltage as your devices.

In the US, this is probably 110-130v while in Europe and the UK it’s more likely to be 220-240v.

Static Current or No Load or Idle Consumption

This is how many amps the power inverter uses with no appliances on it. 

Aim for a low no load level though if it’s a little higher, you can always turn the appliance off when not in use.

Just make sure to install it somewhere convenient unless it has a remote control.

And remember those batteries at night when your solar panels aren’t getting any sunlight!

An inverter with an idle consumption of 1 amp will use say 8 amps overnight but a 5 amp device would use 40 amps in addition to any load running at the same time.

That could be a hefty proportion of your total battery bank.

Efficiency rating

This is the overall efficiency of the inverter. An inverter with a 90% efficiency rating uses 10% more energy than the device its supplying.

The efficiency rating often falls with age so check the specifications carefully.

Safety Features

Most inverters come with at least some safety protection features, offering greater reassurance and protecting the van electrics.

They vary from device to device but here’s a list of common features:

  • Auto cut off, LED indicators and alarms for under and over-voltage protection, over-temperature protection, over-load protection, and short circuit indication.
  • High-speed ventilation fans to help keep the inverter running at a low temperature
  • Ground-fault circuit interrupter (GFCI) protection
  • Remote monitoring

The Best Campervan Power Inverters

BESTEK 300w Pure Sine Wave Power Inverter

This is the best budget campervan power inverter for living in a van.

Ideal for powering small AC appliances like camera battery chargers or laptop, 

It has a continuous power surge of 300W with a peak of 700W. 

Bestek 300w inverter

With 2 AC sockets and 2 USB ports it can charge up to 4 devices at once, though you probably rarely need all this.

It’s no frills so best located somewhere easily accessible to switch it off and on.

Despite its low cost, it still has plenty of safety features designed to protect from over heating or depleting the battery bank too much.

We’ve used this for over 3 years living in the van full time and never needed more.

Renogy 700w 12V Pure Sine Wave Inverter

Renogy is one the most reputable brands when it comes to campervan electrical components and they don’t disappoint when it comes to 12v power inverters.

Renogy 700W 12V Pure Sine Wave Inverter

So much so we have 3 of their products on our best of list.

Their 700w pure sine wave inverter is their smallest model. Budget friendly and packed with safety features, you won’t discharge your batteries too much with any of these Renogy inverters.

This 700w device includes a couple of power outlets and a wired remote control too.

BESTEK 1000w Pure Sine Wave Car Power Inverter 

Stepping up a size, this 1000w pure sign wave inverter delivers pretty much everything you could realistically expect to power off-grid with a reasonable size battery bank.

Bestek 1000w power inverter

With dual AC outlets providing 1000W continuous DC to AC power, surging to 2400W when needed, it’ll keep devices running & charging.

3 external fuses and a built-in cooling fan help prevent overload, overheating, short circuit and low voltage battery shutdown.

Renogy 2000w & 3000w 12V Pure Sine Wave Inverter

Some RV owners and van lifers need big, heavy duty inverters and Renogy is our recommended go to brand.

Physically larger than the smaller devices, both the 2000w and 3000w Renogy inverters and extremely well built.

Renogy 2000W 12V Pure Sine Wave Inverter Charger with LCD Display

They’re packed with safety features including short circuit protection, overload protection for both DC input and AC output and much more, so you can use these confidently in your precious van conversion.

With a long wired remote, positioning the appliance out of the way is a realistic option.

The 2000w model has a peak power surge of 4000w and the 3000w inverters surges to a whopping 6000w.

This should be enough to satisfy the most power hungry devices you’re likely to find in any camper.

Make sure to use our exclusive Renogy discount code when buying direct from Renogy.

Just enter “Mowgliadventures” at the Renogy checkout for an automatic 10% discount off all eligible products.

RV Inverter Wiring Diagram

Here’s a simple overview of an RV inverter wiring diagram.

Below you’ll find the instructions on how to wire an inverter in an RV.

RV Inverter Wiring Diagram
RV Inverter Wiring Diagram

How to Install a Power Inverter in A Camper

Active Time: 30 minutes
Total Time: 30 minutes

No matter the size of your campervan power inverter, the installation is generally the same. This guide shows you how to wire an inverter in an RV, motorhome or camper.

Materials

Instructions

  1. Choose a suitable location for inverter
  2. Secure the inverter to its operating position
  3. Connect the inverter’s chassis earth point to the van’s earth point
  4. Connect DC -ve cable from the inverter to the -ve terminal of the battery
  5. Connect DC +ve cable from the inverter to it’s designated fuse block output
  6. Insert fuse
  7. Switch on device
  8. Using multimeter confirm input & output voltages are correct
  9. Plug in appliance & play

Notes

  • Designated fuse holder - use a spare one in existing block or install a new one. Make sure the cable from the battery to the fuse block is large enough to handle the inverter size
  • Make sure there is plenty of ventilation around the inverter to help keep it cool when in operation
  • Position the inverter as close to the battery as possible to minimise voltage loss
  • This how-to guide provides an informative overview. Always follow the manufacturer’s installation instructions.
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