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The Ultimate Guide to Motorhome Generators

For many, one of the best things about staying in an RV is enjoying some of the comforts of home, like electricity. While many RVers rely on shore power to keep the lights on and the AC humming, when not plugged in a motorhome generator or inverter is required to power your appliances. Read on to learn more about how to use them and why they’re a vital part of a mobile power system.

motorhome generator slid out on hydraulic rails

What Are Motorhome Generators?

A generator is a device that transforms fuel into electricity when traditional power isn’t available. Many people have these in their homes to help during power outages, but they’re also available in more specialized models. Among the generator variations are motorhome or RV generators, which are for RVs and other similar vehicles. These generators allow your rig to receive 110V ( and sometimes 240V) AC power, which many devices require to function without needing a connection to shore power.

→ See our Complete Guide to RV Generators.

What Types of Generators Do Motorhomes Use?

Most commonly, motorhomes use built-in generators that draw from the rig’s fuel tank. They’ll run on either diesel or gasoline, depending on your RV’s needs. The most common built in generator is the Cummins Onan but a few other brands exist like Generac and Power Tech.

cummins inverter generator

If a motorhome does not have a built in generator portable generators can be carried and also run on gas or diesel, but you’ll need to carry fuel and fill them yourself. Solar-powered portable generators are also growing in popularity thanks to their renewable, environmentally-friendly operation.

➔ Curious if one type of generator is better than the other? Find out: Onboard RV Generator vs. Portable: Which Is Better?

What Is the Quietest Generator for a Motorhome? 

As anyone who uses a generator or camped near someone using one knows, they can be relatively loud. This noise can cramp your style on what should be a relaxing camping trip. However, inverter-based motorhome generators tend to be quieter, as they can occasionally idle to lower the overall noise. Cummins onan offers some built-in options that include inverter operation that can idle down and use less fuel and make less noise when under less load.

It may seem counterintuitive but may times the larger built-in generators actually tend to seem quieter. This can be due to the larger size and larger sound dampening, but also the lower tone and operational frequency of the units.

big built in motorhome generator
Surprisingly the large motorhome generators tend to be some of the quietest.

Can You Run a Generator While Driving? 

You can run built-in generators while you drive your rig. Whether you need to power some appliances or get an extra boost from your rooftop air conditioner on hot days, most rigs will have no issues using their generator while driving. In fact, many manufacturers that have inverters as well will recommend you run the generator when driving and operating heavy load appliances. This is because if you run them on the inverter you may inadvertently overload the engine’s alternator and burn it out.

Also, remember however that your generator may have to shut off due to an automatic cut-off when your fuel drops below a certain level. 

Class A motorhome
Built-in motorhome generators are safe to use while driving.

On the other hand, you should generally not use portable generators while driving. You need to safely vent the carbon monoxide and other fumes from the generator’s exhaust. Various logistical reasons also make it a bad idea to run your portable generator while traveling. 

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

How Long Can I Run My Generator?

You can run your motorhome generator as long as you have enough fuel! If your generator draws directly from your RV’s gas tank, it will usually run until your rig reaches a quarter tank. This crucial fail-safe feature ensures you never end up with an empty tank from a thirsty generator. For portable generators, your run time will depend on how much fuel you’ve brought to supply it. For new generators, it may take time to get a handle on how long fuel will last.

With regard to the time of day, some campgrounds have generator hours. This means you will not be able to operate your generator in the middle of the night.

Can You Run an RV Generator While Plugged Into Shore Power?

Many RVers may be concerned about whether they can use these power sources simultaneously. Some may worry about possible damage to their RV, or worse, causing severe potential issues with the power line feeding to your rig. However, your RV is designed to prevent these things from happening.

RVs with built-in generators typically include an automatic transfer switch, which regulates power coming into the rig and prevents multiple sources from reaching your RV’s electrical system and damaging it. This switch also helps avoid the possibility of back-feeding electricity into the shore power line.

Built in RV generator wiring diagram
This is how most built-in RV generators are wired. The 50 amp versions are usually not split-phase and the two breakers are connected together in the generator. The transfer switch only allows one power source to the RV at a time.

If an RV does not have a transfer switch it usually has a plug that the shore power line needs to be plugged into when not in use. This plug acts as a manual transfer switch preventing feeding the RV with two power sources.

Pro Tip: Don’t make dangerous electrical mistakes! Learn How to Not Get Shocked in Your RV.

RV generator Safety Infographic

Does My RV Generator Charge My Batteries? 

Your motorhome generator can charge your RV batteries, making it an excellent way to keep your batteries ready on the go. While your starting battery will charge as you drive, you’ll need to plug your RV into the generator to charge your house batteries. This mimics a connection to shore power, allowing the house batteries that power your lights, water pump, and other crucial features to continue operating. 

We highly recommend making the switch to lithium batteries as it will significantly reduce generator runtime and improve quality of life significantly in an RV.

What Can Motorhome Generators Run?

How much you run on your generator will vary depending on your generator’s capacity. Most typical motorhome generators range from 2,000 to 12,000 watts. This range could mean the difference between running a few devices and appliances and efficiently powering a large Class A or fifth-wheel. 12,000-watt generators will provide the equivalent of a full 50-amp hookup, while you can replicate 30-amp hookups with 3,200-watt models.

Standard wattages include between 60 and 300 for TVs depending on size and style, 800-1,400 for coffeemakers, 200-400 for a refrigerator, 50-100 for a laptop, and 50-300 for gaming systems. Air conditioners typically need between 1500 and 2000 watts each.

portable RV generator
A 2,000-watt portable generator could power some, not all, of your appliances.

How Much Does It Cost to Replace a Motorhome Generator? 

The cost of replacing motorhome generators varies by brand, output, and features. The price also depends on whether you do the work or pay a professional. Generators typically cost between a few hundred dollars and a few thousand, with more powerful models selling for higher prices.

Many RVers will need to budget a few hundred to a thousand dollars for the cost of labor to install the generator, but those who are confident installing the generator on their own can save money. Portable generator owners can also avoid this replacement expense. 

RV Electrical Safety Tips and Recommendations- RV Security and Safety Series Part 3

Do You Need a Motorhome Generator?

You do not need a motorhome generator to enjoy using your RV. Some RVers stay exclusively at parks and campgrounds with shore power hookups, making generators a little-used accessory. Others who don’t mind cutting their power usage may also get away with the charge present in their batteries. 

However, even if most RVers may not need a generator, it’s undoubtedly a handy, standard, and welcome additional feature. Motorhome generators provide campers with something close to total electrical power no matter where they are. It allows the comforts of home at the most remote campsites. At a relatively affordable price, it’s a feature most RVers are happy to add to their on-the-go power system.

onboard RV generator

Looking for a quiet portable generator that won’t keep you or your RV neighbors awake at night? We uncovered Which Generator Is the Best (Quietest) for Camping?

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About Tom and Caitlin Morton

Tom & Caitlin Morton of Mortons on the Move gave up the stationary life for one where they are constantly on the move. They are full-time travelers, television hosts, and digital media producers.
They left their jobs, sold their house and possessions, and hit the road in September 2015 in their full-time “home on wheels”. Since then they have traveled the US, Canada, and even internationally by RV.
Now, they are Discovery Channel & PBS TV Co-stars of “Go North” on Amazon Prime Video, co-founders and instructors of RV Masterclass, and contributing authors for and an Arizona travel guide.

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