Portable vs Built-In RV Generators

Every RV needs a way to make electricity when shore power isn't available. The two paths are a built-in (onboard) generator that's permanently installed in the RV, or a portable generator you carry separately. Both get the job done, but they solve different problems and create different tradeoffs in convenience, power, noise, and cost. Here's how to decide.

Side-by-Side Comparison

Built-In Generators: Convenience at a Premium

Built-in generators — brands like Onan (Cummins), Generac, and Champion — are factory-installed or dealer-installed in a dedicated compartment, usually under the floor or in a side bay. They connect directly to the RV's electrical system through a transfer switch, so when you start the generator, power flows seamlessly to every outlet and appliance. Many can be started and stopped from a panel inside the RV, and some can be operated while driving to run rooftop air conditioners during hot-weather travel.

The biggest advantage is power. Onboard generators commonly deliver 4,000–5,500 watts on Class C and smaller Class A motorhomes, with diesel pushers running up to 12,500 watts. That's enough to run one or two rooftop ACs, the microwave, and other appliances simultaneously. Fuel comes from the RV's main tank (gas or diesel) or the propane system, so there's no separate fuel to store or carry.

The downsides: built-in generators are expensive — a new Onan LP unit typically runs $3,000–$5,000 for the generator plus installation. Maintenance requires access to the compartment (sometimes tight), and if the generator fails, your RV is in the shop. They're also louder at the source than modern portable inverter generators, though the compartment does provide some sound dampening.

Portable Generators: Flexibility and Value

Portable generators — Honda EU2200i, Yamaha EF2200iS, Champion 3400, Westinghouse iGen4500 — are standalone units you store in a compartment, truck bed, or cargo carrier and set up at the campsite. Modern inverter models produce clean, stable power safe for sensitive electronics and run remarkably quietly (the Honda EU2200i operates at 48 dB at quarter load — quieter than a normal conversation).

The key advantage is versatility: a portable generator works at the campsite, in the driveway during a power outage, at a tailgate, or on a job site. You're not locked into one RV. If you sell the trailer and buy a different one, the generator comes with you. Two identical units can often be paralleled together to double output.

The tradeoffs: portable generators require manual setup — you carry it out, position it away from the RV (CO safety), connect the power cord, and start it. In cold or rainy weather, this is inconvenient. Most portable inverter models top out at 2,200–3,500 running watts, which may not be enough to run a rooftop AC and other loads simultaneously (a 13,500 BTU AC draws about 1,200W running but 2,800W on startup). And you need to carry and store separate fuel unless it's a propane model you can connect to the RV's LP supply.

Sizing: How Much Power Do You Need?

Basic boondocking (lights, fridge, fans, charging): 1,800–2,200W portable is plenty. These loads typically draw under 500W continuous — the generator mostly charges your battery bank and runs the converter.

Single rooftop AC: 2,800–3,500W minimum. A 13,500 BTU AC needs about 2,800W to start (surge) and 1,200–1,500W to run. A 3,000W+ portable inverter generator handles this, though it'll run at higher load and consume more fuel. A built-in 4,000W unit handles it comfortably with room for other loads.

Two ACs or heavy loads: 4,000–5,500W minimum, which generally means a built-in unit or two paralleled portables. This is common for larger Class A or C motorhomes and fifth wheels in hot climates.

Noise Considerations

Campground courtesy matters. Many campgrounds enforce quiet hours (typically 10 PM – 8 AM) and some restrict generator use entirely. Portable inverter generators are the quietest option — the Honda EU2200i runs at 48 dB, the Champion 3400 at 59 dB. Built-in LP generators (like the Onan MicroQuiet series) are rated around 52–65 dB, though the compartment dampens this somewhat.

Position portable generators at least 20 feet from the RV and neighboring sites, with the exhaust pointed away from occupied areas. Never run any generator inside an enclosed space — carbon monoxide is odorless and lethal.

The Third Option: Solar + Battery

Many RVers are supplementing or replacing generator use with solar panel kits and lithium battery banks. A 400W solar array with a 200Ah lithium bank can handle most boondocking loads silently and indefinitely in sunny conditions. The generator becomes a backup for cloudy stretches or heavy AC use. This hybrid approach — solar for daily loads, generator for peak demand — is becoming the standard for serious boondockers.