The Complete Guide To RV Generators

While RVs enable us to get away from it all, many of us like them because they offer home comforts while doing it. These comforts include hot running water, comfortable spaces, and electricity. While there are a few ways we can provide power to our RVs, the RV generator is still one of the easiest and cost-effective ways to power your rig.

Almost all RVers will have a generator, but there are many options and types out there. As an electrical engineer, I get a lot of questions about generators, so in this guide, we will be sharing all the primary information you should consider when deciding on the right generator for your RV adventures. 

What Is An RV Generator? 

A generator is any device that generates electricity. Generators could be the alternator in a vehicle’s engine, solar panels on the roof, a wind turbine, or even a fuel cell.

While all these are electricity generators, most of the time, when referring to an RV generator, we are talking about an engine-driven device. These devices run on fuel and generate AC power like you find in your home. For the remainder of this article we will be focusing on generators the use fuel to convert into electricity. If you would like to learn more about solar generators or solar power we have an entire category of those articles on the site.

Some generators are specifically designed for RV’s and are built-in, while others are portable, but they all do the same thing. Anyone can use the same portable generator for backup power in a home for an RV and vice versa.    

For the remainder of this article, we will be discussing Internal combustion engine generators that provide AC power for an RV. 

Why Do You Need An RV Generator?

To maintain all the comforts of home when camping unplugged or off-grid (sometimes called boondocking or dry camping), we need a few things. We are trying to replicate the utilities in a home, so we need water in our tanks, a holding tank for sewer, and a way to provide electricity. The need for electricity is where the generator comes in.  

When running an RV generator can power all the 120 volt plugs in the RV, so you can use the RV just like a home. The generator also charges the RV’s batteries, so when you shut it down, the 12-volt system of the RV keeps operating.  

An RV generator can also run larger appliances that use AC power like an air conditioner and microwave. People will often run an RV generator for a few hours each day to charge batteries and run larger appliances, then shut them down for the night and when not needed. 

Pro Tip: Having an RV generator can help your rig become self-contained. Learn more about What Is a Self-Contained RV and Do You Need One?

Can You Camp Without A Generator?

Yes, an RV is designed to run all its primary systems off its 12V batteries. However, if there is no way to charge the batteries, the RV will not function when the battery dies. Many RVers choose to add solar power or alternator chargers to charge batteries without a generator. 

We made a six-month trip to the arctic ocean, living mostly off-grid without using a generator. Doing this, however, requires designing specialized electrical systems. We also rarely run a generator in our fifth wheel due to our ultimate RV solar build.  

While these are alternatives to generators, most people choose to start RVing with a generator as it is an easy, inexpensive way to get guaranteed power.  

Will An RV Generator Charge The Batteries?

Yes. When an RV generator runs, it powers systems just like when the RV is plugged into shore power. This includes the 12V converter or battery charger. Depending on the RV, this can be a stand-alone unit or built into an inverter charger combination unit.  

The RV batteries provide power for the lights, water pump, and appliances. The battery system keeps the essentials running even without a generator running.   

One recommendation we like to make when running a generator to charge batteries is to add a battery monitor to the system. This device provides an accurate measurement of the battery’s state of charge and can let you know when they are fully charged.

If charging lead-acid batteries, it’s important to get them fully charged, or you risk damaging them. Getting the batteries completely charged may incur extra generator run time. If running lithium-ion batteries, it does not matter when the charger gets turned off. Either way, knowing the accurate state of charge of the batteries is very beneficial for an RV user.  

We recommend the BMV712 battery monitor system for its ease of use and great features. 

Did You Know: You can’t use a generator everywhere you travel. Learn more about California’s Generator Ban.

What Are The Primary Types of RV Generators?

There are many types of generators out there. Some are specifically designed for RVs, while others are not. The two primary categories of generators for RVs are portable and built-in. 

Portable RV Generators

Portable generators are ubiquitous amongst RVers for their low cost. Many travel trailers and fifth-wheel RVs do not have the capability to install a built-in generator, so these portable generators are the only option.

Portable generators have a power output panel on their side that the RV plugs into with its regular shore power cord. Portable generators come in many different types and are used in many various applications, including camping. 

Below are the primary types of portable generators. 

Contractor or Frame Generators

This type of generator tends to be the most cost-effective for the amount of power they provide. Contractor generators commonly provide 3000 to 10000 watts of available power.  

They tend to be open-frame meaning the engine and generator parts are exposed to the air for natural cooling. These generators are also known as contractor generators because construction contractors frequently use them.  

While this type of generator can be used for camping, they tend to be much louder than alternatives. Contractor generators also need to run at one consistent RPM, making them less efficient on fuel unless you are running very high loads consistently.  

If you choose to camp with one this type of generator, keep in mind that many RVers dislike these due to their noise. Be considerate of camping near others with this type of generator and try to run a longer cable and move them further from the campsite to minimize noise.  

Inverter Generators

Inverter generators are more costly than the contractor type and provide lower power outputs but have many other camping benefits. This type of generator tends to be fully enclosed and uses fans to cool the internals.

Inverter generators are usually smaller than contractor types and are available in sizes from 1000 watts to 5000 watts.

The inverter generators’ unique thing is the inverter technology that they run on (More on inverter generators below). This makes them much quieter and more efficient on fuel no matter the size of the load.

Some inverter generators also have a unique ability to be connected in “parallel”, meaning you can make a larger generator out of two smaller units. This parallel connection allows you to run larger appliances when needed or you can save fuel by using a single unit when you require less power. 

Because of these benefits, inverter generators are the best choice for portable generators for most RV travelers.

Pros and Cons of Portable Generators    

Besides their low-cost portable generators are very easy to work on, and the owner can move them away from the RV to minimize noise. Portable generator owners can also use them for other purposes than just RVing, like backup power for a home.  

A generator’s portability can also be its downfall as they are a high theft risk. Because of this, many people like to lock them up when running. Portable generators also have smaller fuel tanks and require filling fuel more frequently.  

Built-In RV Generators 

RV manufacturers typically design and install built-in RV generators as part of the RV’s construction. They are commonly $3000-$8000 to upgrade in the RV’s cost, making them much more expensive. Usually, these generators are located underneath or in the RV’s frame.

Larger fifth wheels and motorized RVs are the most common types to utilize built-in generators. You will commonly see power ratings of built-in generators from 2500 watts to 7,000 watts, but they can be as large as 12,000 watts. 

As the name suggests, built-in generators also mean they are hardwired into the RV, with no plugs required. Hardwired means that when the generator fires up, it automatically powers the rig.

You usually start these generators with the push of a button from inside the RV. You can sometimes even program them to start automatically when the RV needs power. Situations that would use auto-start would be when the batteries run low, or the air conditioner needs to run.  

Built-in generators come in many different sizes and types. Different fuel types like propane, diesel, and gasoline are common. Most of these generators are single-speed, but some offer inverter capabilities like the smaller portable units.

Most built-in generators are designed to power most of the needs of the RV but it depends on their size. The majority of built-in generators only provide one leg of power to the RV (more on this below) 

Pros and Cons of Built-in Generators

Because built-in generators are part of the RV, they tend to have superior sound and vibration dampening built-in. These generators are also very easy to start and do not require leaving the RV to set up. With generator auto start systems, they can also automatically fire up to provide power when needed.

→ Dive Deeper into the pros and cons of On-board generators vs. portable generators.

While quiet and smooth are good, their built-in nature is also a drawback. You’ll almost always feel some vibration in the RV, and the noise level will always be the same as they cannot move. If the wind is blowing wrong, exhaust making its way back into the RV is more common with these generators.  

Sometimes RVers will re-route the exhaust or add a silencer tube that makes it vent out near the roof.

RV Generator Subtypes 

Both built-in and portable generators have multiple subtype options to choose from. These include fuel type, Inverter or fixed speed, and phase/voltage options. 

Generator Fuel Type

RV generators almost always run on gasoline, diesel, or propane, as these are the most common fuel sources in an RV. If a generator is built-in, it usually runs off the primary fuel source for the RV. If installed in a gas coach, it will be a gas generator, and if in a diesel coach, it will be a diesel RV generator.

Built-in generators in trailers are usually gasoline or propane powered. Many trailers do not have gas tanks on board, but most have propane, so it’s a common option to run the generator. 

Portable generators are most commonly gasoline, but some can run on both gasoline or propane. Diesel options are available for portable generators, but they are less common. 

Propane generators tend to have few fuel issues and do well sitting for long periods of time as the fuel will not go bad. Diesel generators are the second most problem-free type of fuel and tend to have the longest life of any generator type. Gasoline generators are known for fuel issues as the fuel can go stale within a few months. We highly recommend that you keep fuel stabilizer additives in gasoline generators.

Inverter RV Generators

The term inverter generator means that it uses electronics to produce the AC power output instead of the generator’s mechanics. These generators usually use a type of DC generator unit that is then converted to AC using an inverter. This is similar to how an inverter works to convert battery power into AC power.  

Non-inverter or mechanical generators need to run a continuous RPM to provide the appropriate power output no matter how much load is on the generator. On the other hand, an inverter generator can run at a lower RPM as the electronics make the appropriate power output.

As the load on the generator increases, the generator will speed up. This makes inverter generators much quieter and fuel-efficient, especially when running light loads. 

Single or Split Phase Generators 

This is a topic that confuses many people, but what it comes down to is if the generator can produce 240Volts or only 120V. A 240-volt generator is called a split-phase generator because it produces 240 volts split into 120 volts twice. You can use this generator type for RVs but may require a special plug adapter.  

A 50 amp RV natively takes split phase power, but most generators are only single phase. A split-phase 240-volt generator is important if the RV requires 240 volts, but this is very uncommon. You can connect most non-split single-phase generators to the RV with an adapter that connects two legs of the RVs input to power the whole RV from one power leg. 

Built-in generators are usually only single-phase as well and do the same power splitting. They typically do this, however, with breakers at the generator. Each breaker provides power to one leg of the power panel in the RV.

Most people do not need to worry about a split or single-phase generator unless they have unique high-power needs. 

Solar Generators

Solar generators don’t really fall into the category of this article as they don’t really work the same way. A solar generator is actually an entire solar power system contained within one single unit. They can be really great to have but frequently don’t fully replace a fuel generator for an RV. Read more about solar generators in our article about them.

RV Generator Safety 

Before you fire up an RV generator, it’s important to know these critical safety tips for operating an RV generator. Generators have fire, heat, and electrical shock hazards associated with them.   

Before using any RV generator, make sure you have a battery-operated carbon monoxide (CO) detector installed and tested in the RV. As generators burn fuel, they emit this very poisonous and odorless gas. Because of wind conditions, it is possible that these fumes could get into the RV and poison you. Also, never run a generator in an enclosed space like a garage or the back of an enclosed truck bed. 

Fuel sources for generators are highly flammable and should be handled and stored with care. Never fuel a running generator and keep ignition sources away from running generators and gas cans.

Always remember to open the fuel vent caps on portable generators before running them. If they are not open, they can both choke the engine out or possibly get hot and boil fuel. I have seen an RV generator fuel tank explode due to a failed tank vent that was not opened.  

Always keep generators away from dry grasses, leaves, or anything flammable. As the generator gets hot, it could start a forest fire, so keep it in a clearing if the area is dry. 

Do not operate portable generators in direct rain or get electrical plugs wet. These can cause shock hazards or damage to the generator circuitry. 

RV Generator Frequently Asked Questions

Now that you have the basics of what RV generators are and how to safely operate them let’s take a look at the most frequently asked questions. 

How do you choose an RV generator?

Selecting the right RV generator is going to come down to determining your needs. Evaluating each’s pros and cons, first decide if you want a built-in generator or a portable one.  

Once you have decided, you then need to figure out how much power you need. You can do this by adding up the wattage of appliances you want to run simultaneously. If you want to run the air conditioning, microwave, and computers simultaneously and charge the RV batteries, you need to add up the loads.   

• Air Conditioner – 2000 Watts
• Microwave – 1000 watts 
• Computers- 150 watts 
• Battery charger – 500 watts 
• This adds up to: 3650 watts

Adding a 20% safety margin to make up for inductive losses and other loads is a good idea. So, you’d require a 4400-watt generator for these loads. Once you add up the loads, you might realize that you could shut the air conditioner down when running the microwave, so you could get away with a 3000-watt unit. 

Once you choose your generator size, it comes down to price, features, and personal choice to pick the right unit.  

How much does a generator for an RV cost?

RV generator prices vary widely from $200 to $10,000. The following list gives a price range for each type of generator. 

Portable Generator Costs

• Contractor/Frame Generator – $200 – $3000
• Inverter – $800 – $3000

Built-in Generator Costs 

• Mechanical – $3000-$6000
• Inverter – $8000 – $13000
• Split Phase 50 AMP – $13,000 – $16,000

What is the quietest generator for RVs?

All generators make noise, which is not ideal, but picking one that makes less noise is great. Luckily there are more quiet generator options on the market than ever before.

In general, inverter generators are the quietest in operation due to their ability to idle the engine down under light load. Midsized 3000-watt range portable inverter generators tend to be the quietest overall.

Couple one of these portable units with a longer 30 amp electric cord to move it away from the RV, and you might not even hear it! 

For built-in generators, there are fewer options, but again the inverter versions will be the quietest. Overall the Cummins Onan series are decently quiet, but it’s also going to depend on the RV manufacturer and how well they sound insulate the generator compartment.

Luckily these generators tend to produce a lower frequency tone that is less piercing, and most people find it less intrusive. 

Can an RV generator run an AC?

Most built-in RV generators are sized to be able to run the air conditioner. When choosing a portable generator, you will need to select one large enough for your air conditioner’s load. Most air conditioners draw 2000-2500 watts, meaning they require a 3000-watt portable generator or larger to run them.  

Some people have managed to run smaller air conditioners with smaller 2000 watt generators by installing soft starts on their air conditioners. This lowers the startup load that will usually overload and shutdown a generator. 

How long can you run an RV generator?

RV generators will run for as long as they have fuel. Some people will run a generator 24/7 when out camping. Run time is dependent only on available fuel.

Portable RV Generator FAQs

One of the most common questions people ask us is how do you connect an RV to a generator. The answer is simple, you take the RV’s shore power cable and plug it into the generator.    

The proper sequence for starting a portable generator is to shut down the RVs main breaker inside then plug the generator in. Start the generator and let it warm up for a minute. Then go inside and switch on the breaker.     

Can you use dog bone adapters to plug in a portable generator?

Yes. In fact, most portable generators will require an adapter to plug into the RV. Some generators will only have a 20 amp 3 prong connection, while others may have a 4 prong twist lock.

Owners can use dogbone or puck adapters to connect the RV’s plug to the appropriate generator plug. 

What is the best portable generator for an RV?

People ask us these questions all the time, and the answers are somewhat subjective.

We have always run Honda portable generators and Cummins Onan built-in generators without much experience with others. Both have performed exceptionally well, even with high run time. While this has been our experience, here is a list of the generators we commonly hear people say they like best. 

Built-In RV Generator FAQs

If you buy an RV with a built-in generator, sometimes it might be hard to figure out how it works. Here are some of the most common questions we get asked about them. 

How do I start my built-in RV generator?

Most built-in RV generators will have a switch somewhere on the control panel to start the generator. This switch is commonly a two-way switch that rocks up and down and should be labeled “stop” and “Start”.

Depending on the generator pushing the switch, the stop direction runs the fuel pump to prime the generator. (Note: propane generators do not have a prime.) The generator should be primed for 10 to 15 seconds (or however long the manual says) if it hasn’t been run in a while.

After the generator has been primed, press and hold the start button until you hear the generator fire. If it does not start, try priming again before restarting.  

If the generator is an inverter type, there is usually an on-off button, but the generator will prime and start.   

Why is there a power delay when I start the generator?

Built-in RV generators have relays that have a built-in delay before connecting power to the RV. This gives the generator a warm-up period to ensure the engine is ready for the load and operating properly before connecting to the appliances. The delay is perfectly normal.

Can I leave my generator compartment closed while running?

Unless you experience the generator’s overheating, they are designed to be run with the compartment door closed.

Built-in generators have fans that draw air up and through the compartment to cool the engine. Sometimes running the generator with the compartment open can actually hinder airflow and cause overheating.    

How is a built-in RV generator wired?

Usually, a built-in generator is wired with one wire connected to each 50 amp RV leg. A single neutral wire runs back to the generator.

In a 30 amp RV, only one wire is connected and the neutral. The wiring is usually connected through an ATS or automatic transfer switch. This switch automatically selects shore power or generator power.  

Can a built-in generator be installed in an RV? 

If your RV does not have a built-in generator, it is possible to add one. This is usually only possible if the RV was originally designed to have a generator installed and space for it. This space is usually in a vented compartment and frequently will have a “generator prep”, meaning it has a cutout for the generator’s exhaust pipe.

→ Onan Generators are a popular on-board generator brand frequently installed in RVs.

You will need to contact an authorized dealer or service tech to determine if you can add a built-in generator. 

RV Generator Maintenance

If you’re going to get an RV generator, maintenance is essential to keeping it running properly. Since RVers only use the generator when camping unplugged, it can go many months without running. All this sitting around can cause all kinds of problems, and there are a few things that can help keep them running smoothly.

One of the best things you can do for your RV generators is to run them regularly. Many RVers call this exercising the generator, and experts recommend you do it monthly. This entails firing up the generator and putting a load on it for 20 minutes to half an hour. This will lubricate the internals of the engine and keep fuel in the lines from going stale.  

Another important thing to consider is adding fuel stabilizers when storing or letting the generator sit. These additives keep the fuel from gumming up or crystallizing.

If you store the generator for an extended period of time without running it, plan to drain the fuel from the lines and possibly “fog” the engine. This entails spraying a fogging fluid into the carburetor or running it in the gas tank. This is a waxy oil that coats the engine internals and prevents corrosion.  

Other generator maintenance will be specific to the generator you have but may include:

• Regular oil level checks
• Regular oil changes
• Air filter cleaning and replacement
• Spark plug replacement
• Fuel filter replacement

If these things are done per the manufacturer’s schedule, many generators will provide thousands of reliable operations hours. 

Basic Generator Troubleshooting

Many Rvers will encounter RV generator troubles at some point. The most common problem is the generator not starting or being hard to start. This is a common problem when the generator sits too long without running.

Many times it’s caused by fuel that has gone bad while sitting. Replacing the fuel is the first recommended step for most generators that are having a hard time starting, but here are some other common things to check:

Fuel System

Is the fuel filter clean and not clogged? Could the fuel pump be not running properly? Is the carburetor clean and not varnished or gummed up?

Ignition system

Is the engine getting spark? 

Oil

Is the oil level low? (many generators have low oil shutoffs) 

Electrical

Other problems can occur with the electrical side. If the engine is running, but there is no power, there are a few things to look into.

First, is there an ATS (automatic transfer switch) for built-in generators, and is it operating? This is a common failure point.

Is there a breaker on the generator panel that is tripped? Has the generator been overloaded and is showing an error? If the generator has been overloaded many times, it must be restarted to operate properly again.  

Remember, generators can be dangerous due to the fuel and electricity. If you are uncomfortable with either of these, find a qualified technician to troubleshoot it for you. 

Environmental Factors On Generator Performance

While generators usually can operate in most conditions, there are some things to keep in mind when running your generator. 

Generators in Rain or Snow and Wind

Most built-in generators are protected from the elements and can be operated in any condition. Wind conditions are the most concerning with built-in generators as exhaust can be blown into the RV with open windows. 

You should always use caution when operating a portable generator in the rain. Most portable generators do not have adequate protection from rain and should not be exposed to water.

You can get generator covers that will keep the generator from getting wet. Even with a generator cover, make sure the generator is not sitting in a puddle. Also, make sure the generator’s electrical plugs are not exposed to water.  

How Does Altitude Affect The RV Generator?

Altitude, or how high above sea level you are, affects all engines. This is because there is less oxygen and lower atmospheric pressure. Because of this, some generators will lose performance when operated at high elevations.

This is most critical for mechanical (non-inverter) generators because they need to operate at the correct RPM. Most of these generators will have an altitude adjustment on the carburetor of the generator. The altitude carburetor adjustment can change this depending on your needs.  

Inverter generators tend not to need adjustment as they change their throttle position to match environmental conditions. This is another benefit of an inverter generator.  

Camping Etiquette with RV Generators 

One of the most important considerations all generator operators need to think about is their noise.

While it’s great to generate power anywhere you go, the noise they create can really detract from the natural experience many people look for when camping. Because of this, try to limit generator run time and choose a quieter model if possible. Don’t run your generator overnight when around others and try to move it further from campsites if portable.  

We have heard many people scoff when they see a camper roll in with a big contractor generator strapped to the back. If we’re all courteous and keep in mind that we need power and quiet, we can all get along. 

Take Your Adventures to the Next Level with an RV Generator!

One of the very first RV investments we made was in a good portable generator, and it changed out RVing experience for the better. Having an RV generator enables you to make the most of your RV when unplugged and allows you to stay comfortable off-grid for longer periods of time.

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