RV Inverters: What They Do and What to Actually Buy

Plenty of used vans come with what the previous owner called an inverter: a modified sine wave unit from a big box store, plugged into the cigarette lighter with an extension cord running to the dinette area. It will charge a phone and little else. Plug in a laptop and it buzzes. Try a coffee grinder and the noises suggest imminent destruction. That is the most important lesson about RV inverters: not all inverters are created equal, and buying the wrong one wastes both money and patience.

What Does an Inverter Actually Do?

Your RV has two electrical systems. The 12-volt DC system runs off your batteries and powers things like lights, the water pump, and the furnace fan. The 120-volt AC system powers household outlets for things like your microwave, coffee maker, TV, and laptop chargers. An inverter converts 12-volt DC battery power into 120-volt AC household power. Without an inverter, your outlets only work when you are plugged into shore power or running a generator.

Pure Sine Wave vs Modified Sine Wave

This is the most important decision and it is simple. Buy a pure sine wave inverter. A modified sine wave inverter produces a choppy approximation of household electricity that works for basic things like charging phones but can damage sensitive electronics, cause buzzing in audio equipment, and make some appliances run hot or refuse to work entirely. CPAP machines, laptop chargers with voltage regulation, modern TVs, and anything with a microprocessor can have problems with modified sine wave power.

Pure sine wave inverters produce electricity that is essentially identical to what comes out of your wall outlets at home. Everything works normally: no buzzing, no overheating, no compatibility issues. Every dollar you spend on a pure sine wave unit is a dollar well spent.

How to Size Your Inverter

Inverters are rated in watts. To figure out what size you need, add up the wattage of everything you want to run simultaneously. Not everything you own, just what you would realistically use at the same time. Here is a typical scenario for us when boondocking:

For most van lifers and travel trailer owners, a 1000 to 2000 watt inverter covers everything. If you want to run a microwave off battery power (which is ambitious but doable with a good battery bank), you need at least 1500 watts and preferably 2000 watts to handle the startup surge. If you never plan to microwave off-grid, a 1000 watt unit is plenty for laptops, phones, a TV, fans, and small kitchen appliances.

Surge Rating Matters

Inverters have two ratings: continuous watts and surge watts. The surge rating covers the brief spike when appliances start up. Motors and compressors draw two to three times their running wattage for a fraction of a second when they kick on. A 2000W continuous inverter typically handles 4000W surge. Make sure your inverter's surge rating can handle the startup draw of your largest appliance.

Installation Basics

A proper inverter installation uses heavy-gauge cables connected directly to your battery bank with an appropriate fuse. The cable gauge depends on the inverter size and the distance between the inverter and batteries. Shorter is better. Most installations use 2/0 or 4/0 gauge cables for inverters above 1000 watts. This is one area where we strongly recommend professional installation if you are not confident with electrical work. Undersized cables can overheat and cause fires.

Position the inverter in a dry, ventilated location. Inverters generate heat during operation and need airflow to stay cool. A sealed compartment without ventilation will cause the inverter to thermal-throttle or shut down, especially on hot days when you need it most. We mounted ours under the bed platform with ventilation slots cut into the platform surface.

Brands Worth Considering

Victron, Renogy, and Giandel all make solid pure sine wave inverters in the 1000-3000W range. Victron is premium but offers excellent monitoring through their app and integrates beautifully with their solar charge controllers. Renogy offers great value and their customer service has been responsive when we have had questions. For budget builds, Giandel provides surprisingly capable units at lower price points.

An inverter is one of those purchases where spending a little more upfront saves headaches for years. Get pure sine wave, size it for your realistic needs plus a small buffer, and install it properly with adequate fusing and ventilation. Your electronics and your peace of mind will thank you.