RV Generator Basics

While some campers see them as an unnecessary luxury, an RV generator can be your lifeline to the modern world whenever you find yourself off the beaten path. If you spend any amount of time boondocking, or even at campgrounds that don’t offer shore power, then a gen set is the only way you’re going to keep your electronic devices going without draining down your house batteries pretty fast. So whether you have kids who you can’t tear away from the Xbox or Playstation for an entire weekend, or you have a medical condition like sleep apnea that calls for a power-hungry medical device, an RV generator will ensure that your batteries don’t run dry when you’re out in the middle of nowhere.

There are a number of different types of RV generators out there, including built-in units and portable generators, and they can also run on a handful of different fuel sources. The three main types of RV generators are:

• gas generators
• diesel generators
• propane generators

What is an RV Generator?

Onan is one of the most commonly seen manufacturers of RV generator sets.

The term “RV generator” typically refers to an engine-generator set that consists of an engine, or “prime mover,” and an electrical generator. The engine component burns fuel, just like the engine in your motorhome, which allows it to operate an electrical generator. The electrical generator can then be used to charge your house or coach batteries or directly power electrical devices. An RV generator can be used to run anything from a video game system to a hair dryer, and a lot of RVers also use them to keep their batteries “topped up” on long trips.

In addition to the basic “prime mover” and “electrical generator” components, RV generators typically have a handful of other associated equipment and accessories. Some type of governor is typically used to keep the engine speed at a constant RPM, and a voltage regulator to prevent potentially dangerous voltage spikes that could damage your electronics. An RV generator will typically also have an exhaust system that includes a muffler and tailpipe — just like the bigger engine that powers your motorhome. An RV generator tailpipe will typically be smaller in diameter than the main exhaust pipe, and they often vent directly underneath the generator.

Integrated RV Generators

A lot of new RVs come with built-in generators that are integrated directly into the rig’s electrical system. These generators are exceptionally easy to use, and they can often be started by simply pressing a rocker switch inside the RV. Motorhomes often have two start/stop switches, one of which is accessible by the driver, and another that is mounted on the range hood, near the levels monitor, or with the electrical panel.

Some built-in motorhome generators include the necessary electronics to automatically switch between shore power and the generator. These are the easiest RV generators to use, since everything switches over automatically depending on whether you are plugged into shore power or running the generator.

In some cases, you have to manually switch between shore power and your RV generator. There are a few different ways that this can be accomplished, but it typically involves plugging your shore power cable into the generator when you want to use it. To make this easier on you, rigs that use this configuration typically have a socket inside the power cable compartment that’s wired up to the generator. If you plug into this before hitting the road, you’ll be able to run the generator to power a TV, or other electronics, while you’re driving.

Portable RV Generators

Any portable gen set can be used as an RV generator.

Rigs that don’t some with built-in generators are sometimes “plumbed” for them. In those cases, there will be a side compartment that’s designed for a generator, so you can install one if you feel like you need it.

If a rig doesn’t have that type of side compartment, then the best option is a portable RV generator. These generators are available in a wide variety of sizes and configurations, and you can actually repurpose just about any  consumer-grade or commercial generator for use in a motorhome — provided you can find space for it. One important thing to remember is that some portable generators are far noisier than gen sets that are designed for RV use, in which case you might find yourself in violation of local campground noise rules.

RV Generator Fuels

While engine-generator sets can run on just about anything — from compressed air, to steam, to sewage — RV generators use three primary fuel sources. Almost all RV generators run on either:

• gasoline
• diesel
• propane

Gas RV Generators

Gasoline is the most common fuel for both built-in and portable RV generators.

Most RV generators consist of a small, four stroke gas engine and an electrical generator. This is due to the fact that most motorhomes run on gas, and it’s easier to draw from a single fuel tank than to introduce a new type of fuel to a coach. A lot of portable RV generators also run on gasoline.

When a built-in generator runs on gas, it will typically have a fuel pump and pickup that are plumbed into the same gas tank that the main engine draws from. In those cases, the generator fuel pickup will typically be installed at a higher level than the pickup from the main engine. This is to prevent an unwary RVer from accidentally running his tank dry and stranding himself. While each manufacturer handles this differently, a built-in RV generator will typically run out of fuel when the tank itself has somewhere from five gallons to a quarter tank of gas left.

Diesel RV Generators

Diesel motorhomes will sometimes have gas generators — which requires a secondary fuel tank just for the generator — but they can also use diesel generators. In that case, the generator will typically pull fuel from the main tank, just like a gas generator in a gas rig.

The main benefit of a diesel generator over a gas generator is fuel efficiency. Diesel engines are more fuel efficient than gas engines, and the same holds true for diesel generator sets. That means you’ll typically burn less fuel to generate the same amount of electricity from a gas generator, which can be important if you’re dry camping. Diesel generators also require less overall maintenance than gas generators, and they tend to last longer.

Propane RV Generators

The least common type of RV generator uses liquified petroleum gas (LPG) as fuel. This is the same “propane” that you use to fill your barbecue tanks and the LP tank in your RV that runs the stove, water heater, and furnace. That means that the fuel source for a propane generator is readily available in every RV — even towables — but it also means that fuel source is needed for cooking, heating water, and keeping the RV warm inside.

The main disadvantage of using LPG as a generator fuel in RVs comes down to energy density. LPG generators are fuel efficient, and they don’t produce the same amount of emissions as gas and diesel generators, but LPG isn’t very energy dense in comparison. That isn’t a big deal for stationary generators that are plumbed into a supply line, but it can become an issue when you’re carrying around a limited supply of LPG.

RV Generator Power Production

Even a large bank of house batteries will only last so long without an RV generator to charge them back up.

In addition to the type of generator and the fuel source, it’s also important to take into consideration the amount of power that an RV generator is capable of putting out. This is typically represented in kilowatt hours (kWh), which just means the number of kilowatts that the generator can produce in an hour.

In order to determine how big of an RV generator you’re going to need, you will have to sit down and make a list of the different electronic devices that you want to be able to run. Find out what the power consumption of each device is, and then think about which devices you might need to use at the same time. If you want to be able to run a television and a video game system at the same time, then add up the power consumption of those two devices. If you’d like to also be able to pop a bag of popcorn at the same time, check the power consumption of your microwave and add that in. The resulting number will be the bare minimum kWh that you’ll need out of your RV generator.

You can run just about anything you can think of with an RV generator, up to and including your rooftop air conditioning units, but only if your gen set can handle the power requirements of your electronic devices.