Kohler · REOZ Series (Diesel Commercial Standby)

Kohler 125REOZJG

125 kW standby / 116 kW prime · Diesel · Liquid-cooled

125 kW diesel commercial standby generator. John Deere-powered mid-range diesel for commercial, healthcare, and institutional applications.

Kohler Kohler 125REOZJG generator — specifications and details
Standby power
125 kW / 116 kW prime
Voltage options
120/208V, 277/480V, 120/240V
Frequency / Phase
60 Hz · 1/3-phase
Engine
John Deere 4045HF285K · 4.5L
CommercialHealthcareGovernment
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Overview#

The Kohler 125REOZJG is a 125-kilowatt diesel commercial standby generator powered by a John Deere engine at 1800 RPM. It uses a brushless rare-earth permanent-magnet alternator with Fast-Response excitation and sustained short-circuit capability up to 300% of rated current for 10 seconds. The unit features integrated environmental containment and is available in sound-attenuated enclosure configurations rated at 71 dB(A) at 7 meters.

Our service experience#

OnPoint services mid-range diesel standby generators throughout Northern California for hospitals, schools, and commercial facilities. The John Deere engine platform in the 125REOZJG shares commonality with the 80REOZJF and 100REOZJF, simplifying parts stocking and technician training across the REOZJ series.

Engineering specifications

Physical

Length
106.3 in
Width
44.1 in
Height
60.1 in
Wet weight
2,702 lb

Acoustic

Enclosure
Sound-attenuated

Fuel system & runtime

Fuel use @ full load
9.9 GPH
Fuel use @ 75% load
7.6 GPH

Photos

Kohler 125REOZJG — product photo

Documents & downloads

Spec sheets & manuals

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Estimate runtime for the Kohler 125REOZJG

Adjust load percent and tank size to estimate runtime. Pre-filled with this model's spec where available.

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Estimated runtime

26.2 hours(1.1 days)

Fuel consumption ≈ 7.64 GPH at 75% load. Estimate based on industry-typical 1800 RPM standby curves (≈0.07 GPH/kW at full load). Actual consumption varies by engine, ambient temperature, fuel quality, and tuning.

Service intervals

Manufacturer-recommended intervals for the Kohler 125REOZJG under standby duty. Field intervals may differ based on load profile, ambient conditions, and fuel quality.

Oil & filter
Every 250 hours or 12 months
Coolant change
Every 3000 hours
Air filter
Every 500 hours
Fuel filter
Every 500 hours
Major overhaul
≈ 15,000 hours
Load bank test
Every 12 months

Common failure modes

What we've seen fail on this platform. Use as a service-planning reference, not a diagnostic — actual failure modes depend heavily on duty cycle and maintenance history.

ComponentSymptomTypical hoursSeverity
Fuel quality / degradationInjector fouling, hard starting, filter clogging4,380+moderate
TurbochargerPower loss, excessive smoke under load12,000+moderate
Battery (starting)Failed to start, slow crank8,760+minor

Frequently Asked Questions

What engine is in the Kohler 125REOZJG?
The 125REOZJG uses a John Deere diesel engine, turbocharged and aftercooled, rated at 1800 RPM for stationary emergency standby use.
What sound level does the 125REOZJG produce?
Per Kohler specifications, the 125REOZJG is rated at 71 dB(A) at 7 meters at full load with the sound-attenuating enclosure.
Does the 125REOZJG include fuel containment?
Yes. The unit includes a 125% oil/coolant containment basin and 110% secondary fuel containment tank with 24-hour runtime capability at prime rating.

Compatible equipment

Transfer switches

More in the REOZ Series (Diesel Commercial Standby)

Kohler's diesel commercial standby series — 10 to 510 kW, John Deere and Kohler engines, built for life-safety loads.

View all 33models in this series →

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