How Do RV Generators Work?

With modern RVs boasting more solar capability than ever, the possibilities for off-grid camping are expanding. But if you want to stay out more than a few days, RV generators are an essential piece of technology you need. Like all technology, they require maintenance and troubleshooting, making it critical you understand how RV generators work if you own or are considering buying one. 

While they aren’t complex, a better understanding of their operation will help you troubleshoot if issues arise. This tutorial will cover all the basics of RV generator operation. 

What Is an RV Generator?

An RV generator is either an onboard (built-in) or portable mechanical device that can be used as an alternative power source for your RV. With the right size generator, you can power all the appliances in a 30 or 50-amp RV. 

In most motorhomes and some larger trailers, you’ll find onboard generators rated to supply power to even your largest appliances. For trailers and motorhomes without built-in generators, you’ll need a portable generator that can handle your appliances with the highest wattage requirements (usually your RV roof air conditioner).

Depending on your trailer’s electrical service requirements, you can explore portable generators below: 

Technician Tip: Study the actual ratings for generator performance, which are typically found in the PDF owner’s manual—not necessarily on the generator housing. The ratings on generator housings can be misleading, but the information you need to find the right generator for your RV is readily available in the owner’s manual for most major manufacturers. 

How Do RV Generators Work?

At the most basic level, an RV generator powers your RV. But how? Here’s a quick synopsis: 

An RV generator has an internal combustion engine that converts chemical energy (stored in the fuel source) to mechanical energy or rotation. Coupled to the combustion engine is an alternator that converts that mechanical energy to electrical energy that can flow to your RV’s breaker panel to feed power to your camper’s electrical equipment and appliances. 

To simplify, an RV generator burns fuel to create electrical energy. That energy is supplied to your RV’s electrical system by plugging your surge protector and power cord (and often an electrical adapter) into the generator. 

Because they are fuel-burning, portable generators should never be used in an enclosed space and should always have plenty of ventilation when in use. 

In a motorhome or towable RV with an onboard generator, these electrical connections are typically part of the RV’s factory construction, removing the need to plug in to use generator power. These designs also typically include an automatic transfer switch that ensures only a single power supply source—shore power or generator power—to the RV’s AC voltage system.

How Long Can You Run an RV Generator?

Most generators can run for as long as they have a fuel supply. Their run time also depends on the load placed on them. The more load (i.e., the more electrical appliances you use at one time), the less fuel-efficient most generators will be. 

That said, here are the advertised run times for some of our most popular portable RV generators: 

In addition to a generator’s rated run time, there’s also the consideration of how long you can run a generator before maintenance is required. That period will depend on the manufacturer’s recommendation. 

For example, the Honda EU3200iAC generator we reviewed recommends changing the oil every 115 operating hours. The manufacturer also offers recommended service intervals for air filter cleaning, spark plug replacement, and other important maintenance tasks. 

For general maintenance, it’s recommended that you run your portable or onboard RV generator for a minimum time period each month, even when your RV is in storage. 

For example, Cummins states that their Onan generators should be operated at 50% load for at least two hours each month. If you aren’t able to run an Onan generator for two hours continuously, you can break it into two 1-hour “exercise” sessions. 

Perhaps surprisingly, non-use is a leading cause of generator failure. Non-use can cause dry starts and moisture accumulation in the crankcase. While better than nothing, running the generator for less than an hour won’t provide enough time at operating temperature to boil off condensation.

Technician Tip: Check with your generator manufacturer for minimum monthly operation recommendations.

Does Your RV Have to Be Running to Start the Generator?

When all systems are working as designed, your motorhome’s engine doesn’t need to be running to start the generator. However, onboard generators require a minimum battery voltage to start—usually at least 12 volts DC. 

If your onboard generator doesn’t start (via the interior switch or a switch directly on the unit), you may need to start and run your engine for several minutes to recharge the house battery required to start the generator. 

How Much Fuel Does an RV Generator Use?

An RV generator’s fuel consumption rate will depend on the manufacturer. Let’s calculate the fuel economy for the five popular generator models listed in our earlier table. We’ve provided these calculations by dividing run time by fuel tank size to achieve an “hours per gallon” metric.

These calculations were made based on a consistent 25% load. Remember that fuel consumption will likely increase with a higher load placed on the generator. 

How Long Do RV Generators Last?

The lifespan of your RV generator depends on how often you run it and how well you practice preventative maintenance. Many RV owners report their generators still running well after 10-15 years. Others report a lifespan between 2,000 and 3,000 hours. 

While it’s hard to give a precise estimate of RV generator lifespan, we can be confident that a well-maintained generator will last longer than a poorly maintained one. Consult the generator’s manufacturer for recommended service intervals, which is easier if you choose a Honda generator due to their smartphone-compatible Honda My Generator app.

Technician Tip: Always read and follow the manufacturer’s instructions for safe operation.

Here are a few more tips to help you extend your generator’s life: 

• Never start or stop a generator when under heavy loads. Power off all major appliances before starting or stopping your RV generator.
• Keep adequate oil in the generator. The ideal oil level is between the ‘Add’ and ‘Full’ labels on the dipstick.
• Perform regular cleaning. The air inlets must be clear, and the air cleaner/filter must be clean.
• Inspect the exhaust system. Visually confirm that all exhaust system pipes are clear and open, not crimped. The exhaust pipe must extend at least one inch beyond the RV’s sidewall for built-in generators.
• Check electrical connections. They must remain tight and be kept free of corrosion.
• Keep the generator compartment door closed (for onboard generators). A generator’s cooling design requires keeping the compartment door closed to prevent overheating.

Read more portable generator safety tips.

What else do you want to know about RV generators? Let us know in the comments below.