Cummins Onan P2500i vs Firman W01785

Comparison Overview

Analysis by AJ Quick

Mechanical engineer and founder of RightGenerator

Key takeaways

• Cummins Onan P2500i delivers 2200 running watts, 500 more than the Firman W01785
• Firman W01785 weighs 45.9 lbs, about 2 lbs lighter than the Onan P2500i
• Cummins Onan P2500i runs 10 hours at 25% load, one hour longer than the Firman
• Both are gasoline inverter generators with clean power for sensitive electronics
• Both carry a 3-year warranty for comparable long-term coverage
• Onan P2500i is slightly quieter at 52 dB versus the Firman's 54 dB

Best use cases

Choose the Cummins Onan P2500i if you need a portable inverter generator that can handle a broader range of tasks. With 2200 running watts, it can comfortably power a small RV air conditioner, a mini fridge, lights, and a phone charger simultaneously. It's a strong pick for RV camping, tailgating setups where you want to run a TV and a blender, or as a light home backup unit during short outages. The 10-hour runtime at quarter load means you can run it overnight without getting up to refuel, which is a genuine convenience for campsite use. At 48 lbs, it's still very manageable for one person to carry, and the 52 dB noise level keeps it relatively neighbor-friendly.

Choose the Firman W01785 if your power needs are modest and you want to save a bit of money and weight. At 1700 running watts, it handles the basics well: charging devices, running a few LED lights, powering a CPAP machine, or keeping a small fan going. It's a solid companion for tent camping, fishing trips, or as an emergency backup for essentials like a phone and a lamp. The 45.9 lb weight makes it slightly easier to load into a truck bed or carry to a campsite. Keep in mind, though, that the lower wattage means you'll need to be more careful about what you plug in at the same time. Running a microwave or a window AC unit would likely exceed its capacity.

Both generators share the same 3-year warranty and inverter technology, so the core decision really comes down to how much power you actually need versus how much you want to spend.

Verdict & recommendation

If your priority is having enough headroom to power multiple appliances or handle occasional higher-demand devices, the Cummins Onan P2500i is the stronger choice. Its extra 500 running watts and longer runtime make it more versatile without adding much weight or noise. If you only need to keep a few small electronics running and prefer to spend less, the Firman W01785 gets the job done for lighter loads.

For most buyers shopping in this portable inverter category, the Onan P2500i offers better long-term value thanks to its greater output and efficiency. But the Firman remains a capable option for anyone whose power demands stay well under 1700 watts. Match the generator to your actual usage, and either one can serve you reliably.