What Size Inverter Do I Need for My Van?

Suppose you have a van build on the go and that you need to supply power to even when you are not hooked up to an electrical grid. In that case, you may be looking into getting an inverter, which converts energy from a battery to supply AC power so you can use large appliances for your van. But what size do you need?

The size of the inverter you need for your van depends on the amount of power you need to generate, but a 2,000- to a 3,000-watt inverter is typically required to generate enough power to supply your entire van. Figure out how much power your appliances produce to know the inverter’s exact size.  

In this article, we will help you figure out how to determine how many watts your appliances produce and how to figure out what size inverter you need for your van. Let us get to it!

What Is an Inverter?

An inverter is a small, rectangular piece of equipment that draws power by a combination of batteries connected parallel. A single 12V or 24V battery may also be used. In a van, these batteries are usually charged by the van, but you can also hook them up to solar panels or gas generators.  

Inverters convert DC (Direct Current) battery power to AC (Alternating Current) energy that can run electronics, medical devices, and other large appliances that typically require connection to an AC power supply.  

Inverters also increase the voltage from 12 volts (standard DC) to higher voltage (usually 120 volts AC). Without an inverter, you will not be able to use devices with two or three-pronged plugs, which are basically all electrical devices. 

When Is an Inverter Needed? 

Some people may not need an inverter to go into their van. It is a personal choice. But some common reasons why a person decides to add an inverter to their van include: 

  • When there is 110/240V gear that requires a high voltage to run 
  • Going off-grid where there will not be a stable power connection  
  • Sensitive medical equipment which requires a stable, high voltage connection 

Some vans have built-in low voltage power systems, so you may not need an inverter. But if you plan to run a lot of powerful equipment using 110 or 240 volts, it is better to have a powerful inverter in your van.  

Purchasing equipment that runs on low voltage power systems is a great way to reduce the amount of energy you need to provide. Some newer vehicles already come with low voltage systems. With these, you typically do not need an inverter since you will not need to power as many high-power appliances. 

Having an inverter is like having a generator, except you do not need gasoline or another fuel source to power your devices. But you will need batteries.  

Many people use a separate (or multiple) battery from their vehicle battery to supply power to their van. Inverters draw the power from your battery to power your large power items.

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Types of Inverters 

When researching inverters, you may come across the terms pure sine wave or modified sine wave. Let us look at the differences between a pure and modified sine wave inverter. 

In basic terms, a pure sine wave inverter provides the cleanest power. The power outputted from a pure sine wave is identical to your house’s energy is called “grid power quality.”

With modified sine wave inverters, the power produced has a less consistent electricity flow, making the power output stepped or squared. You can run into problems trying to power large devices using this type of inverter.  

If you want to power audio equipment, TVs, laptops, LED lights, microwaves, motors, medical equipment, or refrigerators, you will do better with a pure sine wave inverter. 

Modified Wave Inverter 

Modified wave inverters are best for simple electrical items that do not require a lot of juice. This type of inverter works for simple heating devices, such as: 

  • Coffee or teapot 
  • Hair iron 
  • Water boiler 
  • Space heater 
  • Toaster and toaster oven 
  • Incandescent lighting (dimmer switches and power controls can struggle) 

But even with these devices, you can run into problems trying to power using squared sine waves. It depends on your electronics.  

Modified sine waves can power fans, but you are risking an AC power motor malfunctioning and possibly damaging your machine.  

With LED or fluorescent lights, a modified sine wave can cause your bulbs to buzz, overheat, and even quit working altogether.  

Pure Wave Inverter  

Pure sine wave inverters produce “grid quality” power, which is the same as your house’s power. Due to this, the energy produced by pure wave inverters is strong enough to handle more powerful equipment.  

The process of converting DC power to AC is complicated. Even if you are running a pure sine wave, you can still face issues with some appliances.  

You can use a True RMS electrical tester to test your inverter’s output to determine if it will convert enough power to handle your equipment.  

Peak Power vs. Continuous Power 

Some power inverters show outputs with two numbers, separated by a dash such as 200/400. The first number represents the number of watts for running power.  

The second number is the peak power output, which means a short burst of higher watts, which is usually needed to start an appliance or momentarily produce a higher wattage.   

Both pure and modified sine wave inverters should show the peak and continuous power outputs. Knowing the peak power that your devices need to start or keep your equipment running helps when you are trying to decide which inverter to purchase. 

Figuring Out Peak Power 

To determine the peak load of an appliance, you can use a good rule of thumb that states that the rated power consumption of a device multiplied by three is roughly the amount of peak output a device needs to start or cycle. 

However, this is just a guideline to give you an estimate of your equipment’s peak (surge) outputs. Most appliances provide a label stating the peak output. If you do not see this, you can research it online or contact the manufacturer.  

Power Inverter Wattage 

When looking at the different inverter options, one of the most significant factors is the inverter’s wattage. You can get inverters as low as 100 watts up to over 5000 watts. 

The most common sizes used in vans are 2000W or 3000W. RVs with a 30A shore power cannot exceed a 3600-watt inverter. For 50A shore power, you are limited to 12,000 watts. 

Shore power is what you get when you plug into an external power source to charge your onboard batteries. Examples of shore power include campground hookups or a standard outlet at home. You access shore power by installing a battery charger. Some inverters come with a charger and an inverter. 

Knowing how much output power your equipment needs will help you figure out which wattage inverter you may need. You will want to consider the continuous and sustained power outputs to calculate your needs.  

Most devices list their wattage, but if you can’t find the information, you can get an estimate by multiplying volts by amps.  

Some typical items you find in a van include: 

  • Microwave 1000 Watts  
  • Fridge 180 Watts 
  • TV (32”) – 40 Watts 
  • Toaster – 75 Watts 
  • Box fan – 80 Watts 
  • Satellite dish – 15 Watts 
  • Laptop – 75 Watts 
  • Blender – 1560 Watts 
  • Blu-ray Player – 10 Watts 
  • CPAP Machine – 50 Watts 

Wattage Rate/Power Use Cycles 

It would be best if you also considered how your devices’ wattage differs when running versus when it is not.  

Equipment like refrigerators or air conditioners (on energy saver) will only run a few minutes and then shut off.  

But the power needed to generate the wattage necessary for this short time may be the same or less than running a small fan continuously when the motor is always going.  

Inverters have three different possible ratings

  • Surge rating – you want to find an inverter that can retain a surge for at least five seconds. Some of your appliances need a higher surge to start, even if they need less power to continue performing. Examples include your refrigerator or television.  
  • Continuous rating – the continuous rating means the amount of power you will be able to continuously use without causing your inverter to overheat or shut down. 
  • 30-minute rating – this rating is useful when an appliance is only used periodically. For products with a continuous rating lower than the energy needed to power a large item, the thirty-minute rating is quite handy. 

The Inverter Size You Need 

Now that you know about the factors you need to consider before picking your inverter, let us discuss what inverter size would be best for your van. 

For vans that have mostly low wattage products using 12 volts, with little use of 110/240 power, an inverter with 800 to 1500 watts would suffice. You would probably still want to stick with a pure sine wave over a modified sine wave inverter.  

Suppose you want to power an oversized water heater, air conditioning unit, sizable electric heater, or medical equipment that requires grid quality power. In that case, you may want to go up to a 3000-watt inverter or higher, depending on your needs.  

Figure out the size you need by figuring up your continuous loads and the most considerable peak load to determine your wattage needs. Many people often add 20% extra to make sure there is room for error.  

Low Watt Inverters 

There are low watt inverters you can purchase to place in your van. These small, low power inverters are great for cell phones and other small electronic devices when there is not an available DC charger. These inverters have less than 300 watts, but they do not produce pure sine waves.  

Other Factors to Consider 

Other than the amount of voltage you will need, there are a few different factors to consider before purchasing an inverter.  

If noise is something you do not like, you want to be aware that some inverters create a strong buzz while operating. This is more common in the cheaper versions.  

Advanced Features 

You may also want to consider picking an inverter that has a low voltage disconnect that is built in. 

This safety precaution shuts the inverter down entirely before it discharges the battery bank.  

It is also important to pay attention to whether the inverter you are considering has ignition sensing. What this does is keeps the inverter from running unless the engine is cranked. If you want to use your inverter while parked, you may find yourself without power.  

You may also be interested in advanced features such as a metering that is built in to display input and output voltage, load monitoring, and frequency. You can also find inverters that have audio alarms and Bluetooth connectivity.  

Safety Features 

Safety features such as overload trips and over-temperature trips are also beneficial. There is also high battery power off, reverse polarity protection, and short circuit protection options to consider for the safest inverter. But these do come with a higher price tag.  

You can also look for inverters with cooling fans, so you never have to worry about losing power because your unit shuts down to prevent overheating.  

Auto Transfer Switch 

An auto transfer switch is also a feature that you may want in your inverter. With this technology, the inverter automatically detects the generator power, so you do not have two sources of energy coming through the AC distribution panel at the same time. 

When the batteries get too low, the inverter turns the power back on and keeps it running until the batteries are recharged. You keep a full battery bank and constant electricity without having to switch manually.  

Size of Inverter Relates to Size of Battery Bank 

The size of the inverter you choose will also affect your battery bank. If you are going to be using a large inverter and powering large loads for extended periods, you will have to increase your battery bank size. 

You have to consider your current battery bank’s size if you are not going to exchange it for a new one when you install an inverter. You will not be able to run a large inverter if there is a small battery bank that can’t contain the power. 

To determine the necessary size of your battery bank, try this math: 

  • With deep-cycle FLA batteries, multiply the inverter size by 0.67. 
  • If you are using AGM batteries, multiply the total inverter size by 0.33. 
  • For Lithium batteries, multiply by 0.17. 

Upgrading your current battery bank from an FLA to an AGM or Lithium style battery does not always give you more storage space. You are actually just getting the capability to discharge the bank faster without damaging the battery life. 

A few facts to remember are: 

  • Lithium batteries can be discharged quicker without damage than other battery types. 
  • AGM batteries discharge at a higher rate than FLA batteries. 
  • Always make sure you do not exceed the manufacturer’s discharge rate max. 

Once you have the results of the minimum battery amp-hour rating for your battery bank, it is time to decide if you need to replace it or choose a smaller inverter. 

If your calculations show that the amp-hour rating is lower than the amp-hour rating of your battery pack, your current battery bank will work with your chosen inverter. 

However, suppose the amp-hour estimate exceeds your battery bank amp-hour rating. In that case, you will have to decide whether you want to remove items from the load, buy a smaller inverter, or add more same size batteries until the amp-hour rating gets higher than your calculated amp-hour rating minimum.  

You may also decide to change from FLA batteries to AGM or Lithium batteries. Both Lithium and AGM allow a discharge that is much higher for a set amp-hour rating. AGM batteries provide almost twice the amount of maximum discharge as FLA batteries. Lithium batteries offer four times the speed of FLA batteries.

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How to Match Battery Bank and Inverter Size 

After you have calculated the required inverter size based on continuous watts, you will want to divide the inverter size by dividing inverter watts by battery number listed below to get the minimum amp-hour rating. 

  • FLA (Flooded Lead-Acid) – 1.5 
  • AGM (Absorbed Glass Mat) – 3 
  • Lithium – 6 

For AGM batteries, the maximum inverter size is three times the amp-hour rating. With Lithium batteries, it can be up to six times the amp-hour rating of the battery. 

In Closing 

Installing an inverter in your van is an excellent way to power large appliances that require AC output instead of DC. Inverters reduce the need for a generator or other loud device to provide power to your van when not hooked up to an electrical source. The best inverter for a van will be between 2,000 and 3,000 watts, although you may need a lower or higher wattage inverter depending on what you are trying to power.

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