The Kohler KG125 is a 125-kilowatt commercial standby generator — the largest mid-frame unit in the KG gaseous lineup before transitioning to the large-frame KG200+ platforms. It serves larger commercial facilities, campus-scale buildings, and light industrial operations where 80-100 kW of sustained load demands a genset with margin.
Common deployments: full-service hotels with significant HVAC load, large multi-family residential complexes, school campuses, light industrial facilities, and commercial cold-storage operations where gaseous fuel avoids the diesel storage complications.
Three-phase only at this size — single-phase applications should look at the KG100 or below
The KG125 is the right unit when the KG100 is too close to the line. If your load study shows 75-100 kW peak with HVAC cycling or frequent motor starts, the KG125 provides the headroom that prevents nuisance under-frequency trips during transient loading.
The KG125 shares the turbocharged inline-6 architecture with the KG100, just at larger displacement. Service procedures are nearly identical. The slightly larger oil sump means the same 500-hour / 12-month interval but with more oil per change. We see these units primarily in hospitality (larger hotels) and multi-family (150+ unit complexes) where the building's common-area load justifies the step up from KG100.
Service intervals
Manufacturer-recommended intervals for the Kohler KG125 under standby duty. Field intervals may differ based on load profile, ambient conditions, and fuel quality.
Oil & filter
Every 500 hours or 12 months
Coolant change
Every 4000 hours
Air filter
Every 1000 hours
Spark plugs
Every 2000 hours
Major overhaul
≈ 20,000 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.
Component
Symptom
Typical hours
Severity
Turbocharger bearings / seals
Oil in intake, blue smoke, reduced power
12,000+
moderate
Spark plugs / ignition coils
Misfire under load, cylinder dropout
2,000+
minor
Intercooler system
Boost leak, reduced power, hissing
8,000+
minor
Exhaust manifold / turbo gaskets
Exhaust leak, soot staining, ticking
8,000+
moderate
Parts cross-reference
oil Filter
Kohler GM30378
air Filter
Kohler GM62256
spark Plug
Champion RN14YC
starting Battery
Group 31 (recommended)
Frequently Asked Questions
What is the standby power rating of the Kohler KG125?
The KG125 is rated 125 kW standby (113 kW prime) at 60 Hz. It uses a turbocharged 11.1L inline-6, the largest platform in the mid-range KG series before stepping up to the large-frame KG200+ units.
What's the difference between the KG100 and KG125?
Both are turbocharged inline-6 platforms. The KG125 has a larger displacement (11.1L vs 9.3L) providing 25% more power. Choose the KG125 when peak demand is 80-100 kW or large motor-starting is a factor.
What ATS sizing for the KG125?
At 480V three-phase: 200-250A ATS. At 208V three-phase: 400-600A ATS. ASCO 7000 Series or Kohler KCS are common at this capacity.