Onan RV Generator Guide (2026): 9 Models Compared

01Onan RV generators compared

All nine models below are current Cummins Onan RV products. Specs come from Cummins spec sheets and authorized dealer listings. Built-in models (QG and QD series) are sold and installed through Cummins dealers; the portable P-series is sold at retail. Noise figures keep their published test conditions next to the number.

* Distance/load not published for P-series portables. Built-in noise figures are at half load unless noted. Built-in Onan generators are dealer-sold; portables are available at retail.

02How to choose the right Onan

Match the generator to your RV type

Start with what you need to run. A truck camper or small travel trailer with a single 13,500 BTU air conditioner does well on a QG 2800 or QG 4000. Most fifth wheels and larger travel trailers running two air conditioners need a QG 5500 at minimum; heavy two-AC use with electric water heating points to the QG 7000. Diesel Class A motorhomes pair with the QD 6000 or QD 8000, which draw from the coach's main diesel tank so there is no second fuel to manage.

Gas vs diesel: match your RV's fuel

This is the simplest decision in the lineup. Gas motorhomes and towables use QG gasoline models that sip from the chassis fuel tank (with a pickup tube set so the generator cannot drain your driving fuel). Diesel pushers use QD models that share the coach's diesel supply. Diesel units cost more upfront but burn less fuel per hour (the QD 6000 uses about 0.40 gal/hr at half load versus 0.6 for the QG 5500) and typically run longer between major overhauls.

Built-in vs portable

Built-in QG and QD models mount permanently in a ventilated compartment, start from a dash or wall switch, and integrate with an automatic transfer switch. They cost several thousand dollars installed. The portable P2500i and P4500i cost a fraction of that, need no installation, and can also serve at home during outages, but you carry them, fuel them separately, and start them by hand or remote fob. Many owners of smaller trailers find a portable covers 90 percent of their needs at 20 percent of the cost.

Sizing: count your air conditioners

Air conditioning dominates RV generator sizing. Per Cummins spec sheet A-1425, a QG 5500 starts two 15,000 BTU air conditioners with a 1,000W base load at 100 F and 500 ft elevation under test conditions. Real-world results vary with compressor startup demand (a 13,500 BTU AC can surge to around 2,750W on startup; actual surge varies by unit, age, and temperature), ambient temperature, altitude, and other simultaneous loads. BTU rating alone does not determine electrical draw. When in doubt between two sizes, size up: generators last longer and run quieter when not maxed out, and altitude derating (roughly 3.5 percent power loss per 1,000 feet) shrinks your margin in the mountains.

Electrical configuration matters as much as watts. All QG and QD models in this guide output 120V single-phase only. They cannot supply 120/240V split-phase service that a 50-amp RV shore connection provides. A 50-amp RV can run on these generators through its transfer switch in a partial-power arrangement (one 120V leg energized), but this is not full 50-amp service. Never use improvised adapters or bypass electrical protection to work around this.

03The 9 Onan RV generators

#1

Onan QG 2800

Best entry built-in for small trailers and truck campers

• Model: 2.8HGJBB-1120
• Running watts: 2,800W (120V, 23.3A)
• Noise: 70 dB(A) at 10 ft, half load; NPS 60 dB(A) at 50 ft compliant
• Weight: 125 lbs
• Dimensions: 22 x 16.3 x 12.8 in
• Fuel: Gasoline (chassis tank)
• Warranty: 3-year limited

Buy it if: truck campers, pop-ups and small travel trailers with one AC and modest loads.

Skip it if: you run two air conditioners or heavy electric heat; 2,800W will not keep up.

Strengths

• Lightest and most compact built-in here
• Runs a 13,500 BTU AC with baseload to spare
• CARB and EPA compliant in all 50 states
• Lowest installed cost of the built-ins

Trade-offs

• Single-AC ceiling; no headroom for a second
• Fuel consumption not published
• Still needs professional installation

Find a Cummins Dealer

#2

Onan QG 4000

The mid-size workhorse for single-AC trailers

• Model: 4.0KYFA-6747
• Running watts: 4,000W (120V, 33.3A)
• Noise: 68 dBA at 10 ft, half load
• Weight: 172 lbs
• Dimensions: 30.0 x 19.7 x 14.4 in
• Fuel burn: 0.5 gal/hr at 50%; 0.7 gal/hr full load
• Warranty: 3-year limited

Buy it if: travel trailers with one AC plus microwave, TV and charging running together.

Skip it if: you have two roof ACs; step up to the QG 5500.

Strengths

• Comfortable headroom over the 2800 for real-world loads
• Published fuel burn figures
• Long production history; parts everywhere

Trade-offs

• 172 lbs needs a proper compartment and mounts
• Louder than the 5500/7000 per spec
• EVAP model aimed at trailer applications
• KY line being phased out for QG 4000i inverter; still dealer-available

Find a Cummins Dealer

#3

Onan QG 5500

Top pick: the two-AC standard for fifth wheels

• Model: 5.5HGJAB-6755 (EVAP gasoline)
• Running watts: 5,500W (120V, 45.8A)
• Noise: 69 dB(A) at 10 ft, half load
• Weight: 288 lbs
• Dimensions: 33.6 x 22.2 x 16.7 in
• Fuel burn: 0.6 gal/hr at 50% load
• Warranty: 3-year limited + lifetime drive warranty

Buy it if: fifth wheels and large travel trailers running two air conditioners.

Skip it if: your RV is diesel-powered; the QD 6000 is the correct match.

Strengths

• Starts two 15,000 BTU ACs per spec sheet A-1425 (test conditions)
• Best noise figure of the big gas built-ins
• Lifetime drive warranty
• Huge dealer and parts network

Trade-offs

• 288 lbs; permanent install only
• EVAP variant is not EFI (separate EFI variant exists)
• New plus install runs several thousand dollars

Find a Cummins Dealer

Read our full Onan 5500 review for the deep dive: gas vs LP variants, common problems, maintenance schedule, and used-unit inspection checklist.

#4

Onan QG 7000

Maximum gas power for large fifth wheels and Class A rigs

• Model: 7.0HGJAB-6756
• Running watts: 7,000W (120V, 58.3A)
• Noise: 67 dBA at 10 ft, half load
• Weight: 290 lbs
• Dimensions: 33.6 x 22.2 x 16.7 in
• Fuel burn: 0.7 gal/hr at 50% load
• Warranty: 3-year limited + lifetime drive warranty

Buy it if: large fifth wheels and gas Class A rigs that run two ACs plus electric appliances simultaneously.

Skip it if: a 5500 covers your loads; the 7000 burns more fuel for capacity you may not use.

Strengths

• 7,000W handles the heaviest gas-RV loads
• Same footprint as the 5500
• 67 dB(A) at 10 ft per its own spec sheet, quieter than the 5500's 69

Trade-offs

• 290 lbs and higher fuel burn than the 5500
• Overkill for single-AC trailers
• Highest installed cost of the gas line

Find a Cummins Dealer

#5

Onan QD 3200

Small diesel built-in for compact diesel rigs

• Model: 3.2HDZAA-6508
• Running watts: 3,200W (120V, 26.7A)
• Noise: 68 dBA at 10 ft, half load
• Weight: 205 lbs
• Dimensions: 30.5 x 17.3 x 18.0 in
• Fuel burn: 0.3 gal/hr at 50%; 0.4 gal/hr full load
• Warranty: 3-year limited

Buy it if: small diesel motorhomes and diesel truck campers wanting single-fuel simplicity.

Skip it if: your RV is gasoline-powered; get a QG model instead.

Strengths

• Diesel efficiency: 0.3 gal/hr at half load
• Air-cooled; simpler than liquid-cooled diesels
• Shares the coach's diesel tank

Trade-offs

• Some dealers list it as OEM-only; confirm retail availability
• 205 lbs for 3,200W is heavy per watt
• Air-cooled diesel is noisier than liquid-cooled

Find a Cummins Dealer

#6

Onan QD 6000

Best diesel: the diesel-pusher standard

• Model: 6.0HDKAH-1046
• Running watts: 6,000W (120V, 50A)
• Noise: 64 dBA no load / 65 half / 69 full, at 10 ft
• Weight: 420 lbs
• Dimensions: 36.4 x 24.2 x 22.3 in
• Fuel burn: 0.40 gal/hr at 50% load
• Warranty: 3-year limited

Buy it if: diesel Class A and Super C motorhomes running two ACs plus house loads.

Skip it if: your coach is gasoline; the QG 5500/7000 is the match.

Strengths

• Liquid-cooled diesel; long overhaul intervals
• Variable speed saves fuel at light loads
• Full-load noise data published (rare)

Trade-offs

• 420 lbs; needs a serious compartment
• Diesel purchase premium over gas
• Overkill for towables

Find a Cummins Dealer

#7

Onan QD 8000

Big diesel power for the largest coaches

• Model: 8.0HDKAK-1046
• Running watts: 8,000W (120V, 66.6A)
• Noise: 66 dBA at 10 ft, half load
• Weight: 420 lbs
• Dimensions: 36.3 x 23.6 x 22.3 in
• Fuel burn: 0.49 gal/hr half; 1.02 gal/hr full load
• Warranty: 3-year limited

Buy it if: large diesel pushers with three ACs, residential fridges and all-electric coaches.

Skip it if: a QD 6000 covers your loads; the 8000's extra capacity costs fuel.

Strengths

• 8,000W covers three-AC coaches
• Pure sine wave inverter output
• Same 420-lb package as the 6000

Trade-offs

• 1.02 gal/hr at full load adds up fast
• Highest price in the lineup
• Diesel-only; no gas variant

Find a Cummins Dealer

#8

Onan P2500i

Portable Onan power for small trailers

• Running / peak: 2,200W / 2,500W
• Noise: 52 dBA (distance/load not published)
• Weight: 48 lbs (dry)
• Tank / runtime: 1 gal; 10 hrs at 25% load
• Outlets: 120V 20A duplex; parallel capable
• Fuel: Gasoline
• Warranty: 3-year limited

Buy it if: small trailer owners who want the Onan name without a permanent install.

Skip it if: you need to run a roof AC reliably; 2,500W peak is marginal for compressor startup.

Strengths

• Lightest Onan here at 48 lbs
• 10-hour runtime sips fuel
• Sold at retail; no dealer install needed

Trade-offs

• Noise test conditions not published
• No remote start (recoil only)
• Marginal for AC startup

See on Amazon

#9

Onan P4500i

Best portable: remote start and RV outlet

• Running / peak: 3,700W / 4,500W
• Noise: 52 dBA (distance/load not published)
• Weight: 98 lbs
• Tank / runtime: 3.4 gal; 18 hrs at 25%; 15 hrs at 50%
• Outlets: TT-30R RV outlet; remote start
• Fuel: Gasoline (dual-fuel DF variant exists)
• Warranty: 3-year residential / 1-year commercial

Buy it if: trailer owners who want near-built-in convenience without the install bill.

Skip it if: you need automatic start with a transfer switch; only built-ins do that.

Strengths

• TT-30R outlet; RV cord plugs straight in
• Remote start with fob
• 18-hour runtime; longest of the portables
• Wheels and telescoping handle

Trade-offs

• 98 lbs is a two-person lift
• Noise conditions not published
• No auto-start integration

See on Amazon

04Built-in vs portable: the honest math

A built-in QG 5500 plus professional installation typically runs several thousand dollars all-in. A P4500i portable delivers 3,700 running watts for roughly a fifth of that and can also back up your house. What the portable cannot do: start itself when the thermostat calls, switch over automatically via a transfer switch, or run while you drive without setup. Full-time RVers and hot-climate travelers usually find the built-in worth it; weekenders with one AC often do not.

Fuel math matters too. At half load the QG 5500 burns about 0.6 gal/hr of gasoline while the QD 6000 burns about 0.40 gal/hr of diesel. Over 500 generator-hours a year, that is roughly 100 fewer gallons with diesel, which is part of why diesel pushers standardize on QD models beyond just fuel sharing.

05Installation, maintenance and safety

Cummins recommends dealer installation for all built-in models: compartment ventilation, exhaust routing, fuel connections and transfer-switch wiring all have to meet code, and mistakes create carbon monoxide or fire hazards. Budget for the install on top of the unit price and get it quoted before you buy.

Maintenance is non-negotiable. Exercise any Onan monthly under at least half load for 30 minutes; this is the single biggest factor in generator longevity, preventing the stale-fuel and moisture problems behind most "my generator won't start" stories. Change oil and filters at the manual's hour intervals.Carbon monoxide kills: never run any fuel generator in an enclosed space, keep exhaust away from windows, doors and vents, and make sure your RV's CO detectors work.

Affiliate disclosure: RV Solar Power Guide is reader-supported. When you buy through links on our site, we may earn an affiliate commission at no extra cost to you. Built-in Onan generators are sold through dealers; portable models link to retail listings. Recommendations are based on research of manufacturer specifications, not hands-on testing.