Cummins
The volume leader: C series (the commercial workhorse), QSX and QSK (large industrial). Deep parts network, strong resale, the default specification in commercial work. A used Cummins with records is the safest buy in the market.
The best value in backup power — if you know the model families, the inspection, and the sweet spot.
Used generators are the best value in backup power — a low-hour commercial standby set sells for a fraction of new and has decades of life left. They are also the easiest equipment to misbuy: rolled-back hour meters, wrong ratings, tired engines. This guide covers the model families, the inspection, and the sweet spot.
We buy used generators outright — any size. Sell yours →
The volume leader: C series (the commercial workhorse), QSX and QSK (large industrial). Deep parts network, strong resale, the default specification in commercial work. A used Cummins with records is the safest buy in the market.
The premium badge: C-series and the legendary 3400/3500 families. Heavier-built, higher-priced new, and they hold value used — CAT’s dealer network is the best in the business. Older 3400-series sets are famously rebuildable.
Kohler’s KD series plays in large industrial; Generac owns residential/light commercial (Protector, SG series) and has grown hard into industrial. Both hold value well in their segments — Generac’s residential volume means the deepest used market under 50 kW.
Hour meter vs. reality: compare the meter to maintenance records and overall condition — a “200-hour” set with a sun-baked enclosure and original 2008 belts is lying. Cold start: the only test that matters — show up unannounced or ask for a genuine cold start on video; watch for excessive smoke, hard cranking, and how fast it takes load. Under load: a set that idles fine but sags under load has alternator or governor issues — load-bank test results are gold. Fluids: milky oil (coolant leak), fuel in oil (injector issues), coolant condition. Enclosure and wiring: rodent damage, corroded connections, and hacked controls are the hidden killers. Records: oil samples, service history, and load-bank reports separate the known quantity from the gamble.
The most liquid band of the used market is 20–50 kW commercial diesel: small businesses, farms, contractors, municipal buildings. Big enough to matter, small enough to move without a crane and a permit. Supply is constant (facility upgrades, closures, decommissions) and demand is constant (every contractor knows someone who needs backup). Sets in this band with verified low hours and clean enclosures sell fastest and hold value best — they are the working capital of the generator trade. Above 500 kW the market thins and moves slowly; below 20 kW you are competing with new residential units on price.
Standby sets: under 2,000 hours is low; they’re designed for ~200/yr. Prime sets: judge by maintenance records, not hours — a maintained 15,000-hour prime set beats a neglected 3,000-hour one.
Yes — digital meters can be replaced, analogs fail. Cross-check with maintenance records, belt/hose dates, and overall condition.
Only at a price that assumes the worst. A recent load-bank report is the closest thing to a warranty a used set carries.
Wrong rating for the duty, Tier mismatch with the application, no cold-start verification, and missing maintenance records — in that order.
A documented professional rebuild (who, when, what was done) is a plus — it resets the clock on the wear items. An undocumented ‘rebuilt’ claim is worth nothing.
Nameplate (make, model, kW, serial), hour meter, and overall condition. The nameplate is the entire specification.
Call or text 312-880-8174 or use the quote form. Tell us the kW, fuel, hours, and condition.
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