Onboard RV Generators

Which Onan generator fits my RV?

Cummins Onan builds onboard RV generators in gasoline, LP, and diesel versions, from roughly 2,500 to 12,500 watts. Gasoline models such as the QG 4000 and QG 5500 are common in Class A gas coaches and Class C motorhomes. Compact units like the QG 2800i fit smaller compartments. The right Onan generator for your RV depends on three things: fuel type, compartment dimensions, and electrical load. Before ordering, find the model and spec number on the nameplate of your existing generator so you can match it directly.

Should I choose an Onan diesel generator for my RV?

Onan diesel generators (the QD series) are designed for diesel-pusher motorhomes that already carry diesel fuel. A diesel unit draws from the coach's main tank, so you only carry one fuel type. Diesel generators also generally burn less fuel per hour than gasoline units at a similar load. The trade-off is weight and up-front cost: a diesel model is heavier and more expensive than a gasoline generator of the same wattage. If your coach runs on gasoline, stay with a gasoline or LP Onan generator.

What size onboard RV generator do I need to run my air conditioner?

Add up the running watts of everything you plan to power at once, then leave headroom for compressor startup surge. A single 13,500 BTU rooftop unit from the Coleman RV air conditioners line typically needs a 3,600 to 4,000 watt generator. Coaches running two rooftop units usually need 5,500 watts or more. A soft start kit on each air conditioner reduces inrush current and can let a smaller generator start the compressor without tripping.

How does an onboard generator connect to my RV's electrical system?

Generator output runs through an automatic transfer switch, which selects between shore power and the generator before feeding your main breaker panel. From there, your power converter charges the house batteries. If your existing converter is undersized or failing, the 55 amp RV power converters are a common upgrade for coaches with larger battery banks. A hardwired surge protector installed after the transfer switch protects the coach from voltage swings on both shore and generator power. See our Southwire Surge Guard RV surge protectors for hardwired options.

What should I check before replacing an onboard RV generator?

Measure your generator compartment and confirm the mounting rail spacing, exhaust outlet position, fuel line location, and remote start panel compatibility. Onan generators within the same family usually share mounting points, but changing models or fuel types can require new exhaust routing or wiring. Onboard generators ship by freight because of their weight, so check the listing for freight details. Text or call 817-984-1852 with your coach make and the model and spec number of your current generator, and we will confirm fitment before you order.