RV Generator 101: How to Keep the Power On at Your Next Campsite
Onboard RV generators are one of the most valuable features on larger motorhomes, Class C coaches, and many fifth wheels. They provide convenient, integrated power at the flip of a switch, allowing you to dry camp or boondock with confidence. In this RV Generator 101 guide we cover the basics every owner should know: types and sizing, safe operation, setup at the campsite, simple maintenance for long-term reliability, fuel management, and best practices for keeping the generator in good shape and running efficiently.
Whether you are new to onboard generators or looking to improve your current setup, these practical tips will help you keep the power on with more confidence and less guesswork.
Why Onboard Generators Are Essential
Onboard generators give you independence from shore power. They power high-draw appliances like air conditioners that house batteries and solar alone cannot sustain for long periods. They quickly recharge the house batteries when solar input is low and keep the refrigerator, lights, microwave, and electronics running smoothly.
Most onboard units are diesel powered for efficiency and torque, though some gas or propane models exist. They integrate with the RV’s electrical system through an automatic transfer switch, so the coach seamlessly switches between shore power and generator power. For RVers who frequently dry camp or travel to remote areas, this built-in capability is a major convenience compared to portable units that require setup and storage.
Typical sizes range from 3,500 to 5,000 watts for smaller Class C coaches up to 7,500 to 12,500 watts for large Class A motorhomes with multiple air conditioners. The generator is sized by the manufacturer to match the coach’s 30 or 50 amp electrical system and expected loads.
Understanding Your RV’s Power Needs
Before relying on the generator, know what your RV actually requires. A 30 amp RV safely supports about 3,600 watts continuous. A 50 amp RV can handle more across two legs, but you still size the generator based on simultaneous loads rather than maximum theoretical capacity.
Common loads include:
Air conditioner (13,500 or 15,000 BTU): 1,200–1,800 running watts, higher surge on startup
Microwave: 800–1,200 watts
Refrigerator: 150–400 watts
Lights, TV, and chargers: 100–300 watts total
Water pump or furnace fan: 50–200 watts
Start the generator and turn on the largest load first, usually the air conditioner. Once it is running steadily, add other appliances gradually. Avoid starting everything at once. Monitor for overload indicators and stay within safe limits. Many RVs have load management features that help prevent overloads.
For typical weekend or week-long trips you do not need to run the generator continuously. Run it for a couple of hours in the morning to charge batteries and cool the refrigerator, then switch to battery power for lights and fans. Run it again in the evening if needed. This approach saves fuel and reduces noise while keeping the generator in good running condition.
Think in terms of priorities. Cooling, refrigeration, battery charging, and basic cooking needs usually come first. Hair dryers, electric space heaters, coffee makers, and multiple kitchen appliances can create heavy loads quickly, so turn one item off before turning another one on when needed.
Safe Operation Guidelines
Safety is the top priority with any generator. Onboard units are factory installed with proper compartment ventilation and exhaust routing, but you still must follow basic rules.
Never operate the generator in an enclosed space or if the exhaust is blocked. Carbon monoxide is colorless and odorless. Every RV should have working CO detectors. Test them monthly and replace the units on the manufacturer’s schedule.
Follow campground quiet hours. Many parks restrict generator use to specific daytime hours. Some primitive areas ban them entirely. Check rules before starting.
Keep the generator compartment clean and free of debris. Ensure all access doors are properly closed during operation to maintain safe ventilation and noise levels. Have a Class C fire extinguisher rated for electrical fires accessible.
Pay attention to wind direction and nearby openings as well. Exhaust can drift toward slide-outs, windows, roof vents, or a neighboring campsite. If you notice exhaust odor, shut the generator down and correct the situation before continuing. Never ignore a carbon monoxide alarm, even if you think it may be a false alert. Move everyone to fresh air first, then troubleshoot the cause.
Setting Up and Starting the Generator
Onboard generators are designed for easy use. Park on reasonably level ground for best engine lubrication. Open the generator compartment if required by your model and visually inspect for any issues.
Check the engine oil level before every extended use and confirm fuel availability. Most diesel and gas onboard generators draw from the motorhome’s main fuel tank through a pickup tube that stops drawing fuel at approximately one-quarter tank. This helps prevent you from running the main fuel tank dry. Propane models simply need a full tank with the valve open.
Start the generator using the switch inside the coach or on the generator panel. Most units have a preheat function for cold starts on diesel models. Let the generator warm up for one to two minutes before adding major loads. Turn on the air conditioner first, wait until it is running steadily, then add other appliances.
Monitor the load. Many control panels show voltage, frequency, and load percentage. A simple outlet monitor, often called a voltage/frequency tester or Kill-A-Watt style device, can also help you watch Hertz and voltage stability. Stay under 80 percent capacity for best performance. When finished, turn off appliances first, let the generator run briefly under no load, then shut it down.
Simple Maintenance for Long-Term Reliability and Efficiency
Keeping your onboard generator in good shape is one of the best ways to ensure it starts reliably and runs efficiently for years. A few regular habits make a big difference.
Check the oil level before every extended use. Low oil can cause serious damage. Change the oil and filter after the initial break-in period (usually 20 to 50 hours) and then every 100 to 150 hours or annually, whichever comes first. Use the exact oil and filter specified in your owner’s manual. Fresh, clean oil helps the engine run cooler and more efficiently.
Inspect the air filter regularly and clean or replace it as needed. A dirty filter restricts airflow, reduces power output, and makes the engine work harder, which increases fuel consumption. On gas models check the spark plug per the schedule. Diesel models require attention to fuel filters on the recommended interval.
Exercise the generator monthly. Run it under at least 50 percent load for two hours even during storage. This keeps fuel from gumming up in the system, circulates and conditions the oil, charges the starting battery, and prevents moisture buildup. Regular exercise is one of the easiest ways to maintain smooth, efficient operation.
Use fresh fuel and follow the manufacturer’s storage recommendations if the RV will sit for an extended period. Keep the generator compartment clean and dry, and follow the manufacturer’s winterization steps before long-term storage. These simple habits prevent many common starting and performance issues.
If the generator fails to start, common causes are low oil, old fuel, a dirty air filter, or a weak starting battery. Address these first.
Keep a simple maintenance log in the coach. Record the date, hour meter reading, oil changes, filter changes, and any unusual behavior such as hard starting, surging, smoke, vibration, or unexpected shutdowns. That record helps you stay ahead of service intervals and gives a technician useful information if professional service is needed. It is also helpful when selling or trading the RV, because it shows that the generator has been cared for consistently.
Fuel Management Tips
Onboard generators typically use the same fuel as the coach engine, which simplifies logistics. Monitor your coach fuel gauge and plan refueling stops before the tank drops too low. Propane models use dedicated tanks and need the valve open with adequate supply.
To run efficiently, use the generator during cooler parts of the day when the air conditioner does not have to work as hard. Run it to recharge batteries and bring the fridge and freezer back to temperature, then switch to battery power for lights and fans when practical.
Noise and Campground Etiquette
Respect quiet hours at every location. Many parks limit generator use to daytime hours. Position the exhaust away from neighboring sites when possible, and plan ahead if you expect longer runtime. Well-maintained onboard generators are relatively quiet, but courtesy still matters.
Final Thoughts
An onboard RV generator is a powerful tool for comfortable, flexible travel. Keep it simple: know your power needs, follow safety guidelines, perform basic maintenance on schedule, and be considerate of campground rules. With a little attention, your generator can provide dependable power for overnight stops, long boondocking weekends, tailgates, travel days, and emergency situations when shore power is not available.
Before your next trip, check the oil, exercise the unit, and test the system.
If you have any questions or need generator maintenance completed, come check us out at one of our Great American RV SuperStores locations or put in a service request at GreatAmericanRV.com.
