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How Good Are Cummins Onan Portable Generators?

    Whether you’re concerned about blackouts, like to hit the road in your RV, or enjoy heading out into the country for a weekend of camping or fishing (or both), a portable generator is an absolute essential, but there are so many options that choosing your portable power pal can be tricky.

    How Good Are Cummins Onan Portable Generators

    One – or should I say two? – brands that might have caught your eye are Cummins and Onan.

    The Prince of the portable generator world, the company formerly known as Onan, decided to rebrand as Cummins in July 2017, but the big change is yet to really yet to take, mostly because the company now uses Onan as a model prefix, so you’ll see it on the box of all their generators.

    But convoluted backstory aside, you came here to see if this brand produces high quality portable generators, and that’s exactly what I tasked myself with finding out.

    After a lengthy testing period, I’m finally ready to pass on what I learned to you!

    The Cummins Onan Contenders

    I decided that reviewing one generator simply wouldn’t suffice, so I picked up two of Cummins Onan’s most popular portable generators and put them through their paces. The two competitors were…

    My Approach

    In order to gain a better understanding of this brand’s output, I ranked each of their contenders out of 5 in the following 5 categories:

    • Design & Build Quality
    • Compatibility
    • Portability
    • Running Volume
    • Value for Money

    I then tallied up these scores for each generator to give them an overall rating out of 25, before adding up their corresponding categories to give Cummins Onan a company-wide score in each field.

    Finally, I combined the overall scores of each generator, as well as the result from an additional 5-point round on warranties, to give Cummins Onan a total score out of a possible 55.

    Let’s get to it!


    Cummins Onan P4500i

    The Gist

    The P4500i is one of Cummins’ premium portable models, often touted as the best small inverter generator on the market.

    With a 3.4-gallon tank, it offers 3700 running watts and 4500 starting watts, runs at a consistent 60 Hz AC frequency, and tops out at 30.8 running Amps.

    During my tests I found that it performs to spec and can start a 15K BTU A/C system, run plenty of lights, a refrigerator, and a microwave simultaneously with a little headroom to spare.

    Who Is The Cummins Onan P4500i For?

    Looking at the outputs on the control panel, it’s clear that the P4500i was created with the avid RV adventure in mind, but it’s a very versatile machine that would suit pretty much any wandering soul wishing to take some home comforts with them into the wild.

    Design & Build Quality: 5/5

    Out Of The Box

    The P4500i looks absolutely stunning right out of the box, but you have to follow a few steps before you can fire it up, i.e. installing the battery in the back cavity and fitting the panels over the zones that arrive open — I had it up and running in about 5 minutes.

    The battery cavity looks a little roomy at first, but this is so you have space to get your hand in and install it.

    Once all the wires are hooked up, an integrated strap locks the battery in place preventing any problematic rattling when moving the generator.


    You’re spoiled for choice when it comes to ignition, as you have an electric start button on the control panel, a pull-start on the side of the unit for manual operation when the battery dies, and a key fob you can use to turn the generator on and off remotely, something I was far too excited about.

    Neither the electric nor remote starters work on the very first push, but don’t panic; the P4500i just needs a few seconds to channel the fuel into the carburetor.

    Once the gas had circulated, it started immediately every single time during my tests. It’s worth mentioning that the pull-start is silky smooth as well — Very easy on the shoulder!


    The reason behind such effortless manual operation is no doubt the 224cc, 4-stroke, OHV motor. For the uninitiated, OVH is the abbreviated form of overhead valve, which is an optimized valve orientation that increases fuel efficiency.

    As for who makes Cummins’ motors, they take care of every last detail in-house, meaning they maintain ultimate control of QC, a personal touch that really pays off.

    Data Center

    All running information is accessed via the interactive LED display. With just a couple pushes, you can cycle through wattage output, remaining runtime, and current load.

    The figures on the display are nice and bright as well, so you won’t need a flashlight to check up on operations after dark.

    You’ll also find an electric reset button on the interface, so if you ever run into any problems that trigger an auto-shutdown, you can get it up and running again in no time. 


    It has an all-metal, 3.4-gallon gas tank, and during my tests, I clocked capacity in at 18 hours under a 25% load, meaning one tank will most certainly last a full day, no matter how hard you’re pushing this generator.

    However, if you need more power than a single P4500i can supply, these units are chainable in parallel, so you can effectively double your output!


    I hooked up the P4500i to an oscilloscope to peep at its waveform modulation, and what I found was incredible.

    The inverter technology is capable of producing an almost seamless, house-grade sine wave, meaning it can be used to power all the famously troublesome electronics that don’t usually play nicely with generators.


    I don’t have a bad word to say about the enclosure of this Cummins generator. The plastic is super thick and robust, and the metal control panel adds extra protection to the electronics within.

    Compatibility: 5/5

    Cummins packs a lot into the control panel of the P4500i, including two 120 V AC outlets for most of your power needs on the go, and two USB ports for charging small, sensitive electronics like your smartphones and tablets.

    But, for me, the unique and most impressive addition is the RV-ready 30 A TT-30R outlet, meaning you can link this generator up directly to your RV without any adapters whatsoever!

    You’ll also find some smaller parallel ports that you’ll use to chain two P4500i generators together for a maximum 50 A output.

    And last but not least, you have a battery charging port so you can keep the internal SLA battery juiced, but you may never have to use it, as this baby charges itself once up and running.

    A single standard DC port would have been nice, but remember, this generator is aimed at RV-heads who wouldn’t find much use for such an addition, so I’ll let it slide.

    Portability: 5/5

    Weighing just over 100 lbs, the P4500i can be a challenge to lift (I’d recommend utilizing the lateral handles and asking for help when placing it in or removing it from your trunk or RV), but once it touches down, getting from A to B couldn’t be easier for two reasons.

    The first reason? The fantastic puncture-resistant wheels. They’re insanely strong and the aggressive tread helps them glide through challenging terrain, precisely what you need to navigate a torn-up site after peak season.

    And the second reason is the telescopic handle on the other side of the unit, so you can walk the P4500i around like luggage.

    I was a little worried that a telescopic design wouldn’t be quite as hardy as a foldaway handle, but so far, it’s proving to be a reliable asset.

    Running Volume: 5/5

    One of the things that really struck me during the testing phase was just how quiet this thing is.

    Maxed out, you’re looking at something to the tune of 68 dBA when you’re right on top of it, and roughly 64 dBA when standing about 4 feet away, both of which are respectable volumes.

    Eco mode takes things even further, cutting the running volume to 63 dBA.

    However, keep in mind that I was outside during these volume checks and there was a lot of ambient noise around. In perfect test conditions, it can go as low as 52 dBA, making it the joint-quietest 4500-watt portable generator on the market.

    Value For Money: 3/5

    Let me just preface this section by saying that the P4500i is incredibly well-priced, but remember when I said it was the “joint-quietest” option on the market?

    Well, the other is the Westinghouse iGen 4500, and guess what… Besides the colors and decals, these generators are nearly identical, yet you can pick up the Westinghouse version for a few hundred bucks less.

    I did discover that the P4500i has a slightly superior inverter, enabling a more diverse load, but whether that’s worth the excess is up to you.

    Verdict: 23/25


    Cummins Onan P2500i: Review

    The Gist

    With the Onan P2500i, Cummins attempts to serve up all the excellence of the P4500i in a smaller form factor and with a lower output, so those of us with less of a power burden can save a few bucks by scaling down our purchase.

    Bringing 2500 peak watts and 2200 running watts to the table, it’s ideal for all our smaller electrical applications while we’re on the go.

    Who Is The P2500i For?

    Whereas the P4500i was relatively RV-centric, the P2500i seems to have rather loose tailoring in that it doesn’t lean any one way.

    It’d be just as good a weekend camping supplement as it would a reliable essentials back-up during a power outage. 

    Design & Build Quality: 5/5

    Out The Box

    Unlike its bigger sibling, the P2500i arrives fully assembled and ready for action right out of the box, a real bonus if you’re not too familiar with generators and batteries.


    With the P2500i, you get the electric start on the front – just as you do with the P4500i – and the pull start is there on the side too, meaning you can fire it up even when the internal battery has run out of juice, but you do not get the snazzy key fob remote starter.

    As that’s really just a nice-to-have, it’s not a big deal at all, especially as the electric starter and pull-start are exceptional, sparking the P2500i to life first time every time.


    As mentioned in the earlier review, Cummins handles all of their own motor development, so you get a very impressive 3.4 HP, 98cc OVH, 4-stroke engine, which, again, makes for higher efficiency.

    It also helps to stabilize the output of this model and maintain amperage over time and distance.

    I forgot to mention this earlier, but the 4-stroke blueprint is a much more fuel-efficient option, as it only consumes gas every fourth stroke, and perhaps best of all, they’re maintenance-free contraptions.

    So, although I haven’t spent months with this generator, it has what it takes to stand the test of time, as evidenced by a number of glowing follow-up reviews you can check out on YouTube.

    Data Center

    The data center is exactly the same as the LED one on the P4500i. It displays wattage output, remaining runtime, and current load, and you can cycle through these datasets using the little button beside the display.

    The LEDs are just as big and bright as those on the larger model, so visibility is always pristine no matter the light conditions, which I’d consider particularly handy for camping expeditions.


    The all-metal tank can accommodate 1 gallon of gas, which emptied out after 10 hours constant runtime at 25% load during my tests, and, just like its larger sibling, this generator can be chained with another P2500i to send your output through the roof.


    As you’d expect, the inverter technology within the P2500i is identical to that in the P4500i, so it gave me the same pristine sine wave on my oscilloscope.

    This of course means that the power is nice and clean and can be used to power some typically finicky electronics without any grief.


    I was equally impressed with the enclosure, as it seems incredibly hardy, and after tipping the generator back and forth a little, I couldn’t hear any loose components within, and when I actually opened it up to take a look around, everything was very snug and secure.

    Compatibility: 5/5

    You get 4 dust-protected outlets with the P2500i, two of which are fantastic 2.1 A, 5 V USB ports for charging small electronics effortlessly. The other two are as follows:

    • 1 x 12V 8A 
    • 120V 20A 5-20R

    You also get those handy chain ports for running two P2500i generators simultaneously in parallel.

    Portability: 5/5

    With a dry weight of 48 lbs, I’d consider this generator highly portable. I mean, it’ll definitely give you a dead arm if you carry it over long distances, but in terms of loading and unloading, it’s not a bother at all.

    And being that it only measures 19.75 x 10.5 x 18.25”, it doesn’t hog too much space either, meaning you can stock up on more snacks and supplies for the journey ahead.

    Running Volume: 4/5

    Despite being a less powerful unit, the P2500i can only match the 52 dBA minimum of the P4500i, so I’m deducting a point, but this is still insanely quiet.

    Value For Money: 3/5

    When it comes to the P2500i price tag, we see a similar situation as we did with the P4500i and equivalent Westinghouse generators.

    The Westinghouse iGen2500 has an identical spec sheet as the Cummins Onan unit, but it can be snagged for a much lower price tag.

    Much like the P4500i, the inverter tech in the Onan is superior, and on the Westinghouse, you don’t get the cycle button on the LED display, but other than that and a small discrepancy in the USB voltage, they’re the same generator at vastly different price points.

    Verdict: 22/25

    Cummins Onan Warranties: 2/5

    Cummins Onan offers a 3-year limited warranty on all of their generators, which is suboptimal at best, as the industry standard is 5 years.

    The Final Verdict

    Overall, I think Cummins Onan generators are some of the best on the market outside of the truly premium Honda-grade options.

    Both of the units I tested impressed me in near enough every category, and even though they’re expensive compared to their Westinghouse counterparts, the small extras go some way in legitimizing the Cummins premium.

    Although the low-oil and overload protections worked perfectly in both units, I’d like to have seen a CO auto shutdown too, as it’s slowly becoming the standard with modern generators, but as long as you’re using them responsibly, you’d never need such a safety protocol.

    I’ve heard some users complaining that the gas cap is fiddly, which it kind of is, but once you’ve got the knack, it’s not a problem. Besides that small irk, I think these generators really are a cut above the rest.

    Let’s check out the final, company-wide scores!

    • Design & Build Quality: 10/10
    • Compatibility: 10/10
    • Portability: 10/10
    • Running Volume: 9/10
    • Value for Money: 6/10
    • Warranty: 2/5

    This gives Cummins Onan Generators a company-wide total of 47 points out of a possible 55.