How to Figure Out What Size Inverter Works for Your Needs

Published Categorized as RVs

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An inverter is an essential part of any RV electrical system and in most cases, you’ll find that one has already been installed in you rig by the manufacturer. Simply put, an inverter takes the 12-volt DC power from your RV batteries and electronically changes it to 120-volt AC that operates things such as televisions, personal computers or various cooking appliances. Many people confuse the inverter with the converter, which reverses the inverter process and takes a 120-volt AC current and reduces into a 12-volt power supply.

In this article, we’ll look at whether you need an inverter and why you may need one. We’ll also examine the size of the inverter you’ll need based upon the amount of power you want to convert from your 12-volt power supply into 120-volt to adequately supply the power to those appliances you deem necessary to keep functioning.

Understanding the difference between AC and DC power supplies

The biggest difference between AC or alternating current, and DC or direct current power is the direction that the electrons flow. The power source and its supply are also different. Since electricity usually must travel great distances through transmission lines from power suppliers, AC is the preferred method since it loses less voltage (known as line loss) on its journey to your home or business.

When electricity leaves a power station it does so at extremely high voltage. This voltage needs to be filtered down before you can use it, so it flows to substations where the voltage is reduced and then flows though smaller transmission lines that feed businesses and homes. Along the way, it flows through transformers which can either increase the voltage lost through line loss or decrease the voltage flowing into homes and businesses depending upon how much power they will need.

DC current flows from positive to negative terminals in one direction which is what batteries are designed to disperse and that’s why your car battery has two terminals as do batteries used for home electronics such laptops, cell phones and various other devices. Also, most transistors require a DC power supply which is why your cell phone charger or laptops plug into AC power outlets, but the power is converted to DC before it enters your electronic product.

Why do I need an inverter?

An inverter is good to have installed in your RV regardless of where you camp because you never know what can happen. For example, many times when I was staying in a campground with full hook-ups, the campgrounds power supply would shut down due to weather, but I was still able to draw power through my rigs house batteries. So, if you’re like me and like to boondock or camp in primitive campsites that don’t offer electrical hookups, but you still want to power items such as an air conditioner, microwave oven, television, coffee maker or a computer, then you’re going to need an inverter. Typically, these items don’t operate from power supplied by your on-board batteries or solar panels alone because they supply 12-volt DC. Because these items need 120-volt AC, you’re going to need an inverter.

What size inverter do I need?

This really depends upon the amount of power you need to operate the appliances, tools or electronics that you deem essential at any given time. For example, many smaller RVs have 12-volt refrigerators that always drain your DC power supply so it’s important that you understand how much voltage you’ll need.

To do this, look at the specifications for any appliance you intend to have drawing power and add those wattage figures together. Be sure to add 20-25% onto this total sum because pumps, air conditioning units, heaters, microwaves and some tools have high surge requirements to get them started. In short, be sure you include these figures in your final calculation.

Be sure to use the surge rating of all the equipment to size your inverter. It’s best to buy an inverter that has a continuous rating that matches the surge total of all equipment and then add another 20%. For example, one common equation is this example. If the total appliances running at the same time including the surge is 3,600-watts but the running watts are only 2,000-watts. You would get an inverter that is 3600 x 1.20 which equals 4,320-watts. Since inverter manufacturers don’t build an inverter with that exact wattage, you’d be well advised to step up your inverter size and purchase a 5,000-watt model.

Final thoughts

Probably the most important part of determining what size inverter you’ll need when you’re off the grid is understanding the power draw that is required when you’re using your inverter. Another important factor is knowing how much battery supply you need to store the electric needed to power essential items you deem necessary.

As a rule, your RV batteries are charged by your tow vehicle or motorhome/van when you’re driving down the road. However, when boondocking without another source of power to replenish your battery supply, it’s likely that you will drain your power supply quickly and you’ll need another supply of power such as a good generator.

Thanks again my friends. As always, stay safe, stay healthy and always enjoy that journey.

By Brian

Born and raised in Michigan, contributing writer Brian C. Noell is a retired hospitality industry professional that now works remotely as a visual artist, writer and photographer as he travels around the United States in an RV with his dog Lizzy, an eighty pound Appenzeller hound dog.