Generac · MD Series (Modular Diesel)

Generac MD1250

1250 kW standby / 1125 kW prime · Diesel · Liquid-cooled

1250 kW modular diesel standby generator system. Factory-paralleled configuration with Mitsubishi 49.0L V12 engine for N+1 redundancy.

Standby power
1250 kW / 1125 kW prime
Voltage options
277/480V, 346/600V
Frequency / Phase
60 Hz · 3-phase
Engine
Mitsubishi S12R-Y2PTAW-1 · 49L
EPA / Emissions
Tier 2
Alternator
Generac K2112064N22

Overview#

The Generac MD1250 is a 1,250 kW modular diesel standby generator system powered by a Mitsubishi S12R-Y2PTAW-1 49.0-liter turbocharged and aftercooled V12 engine. This megawatt-class modular unit is part of Generac's Modular Power System (MPS) platform, factory-configured with integrated paralleling controls and the InteliGen NT controller for automatic load sharing and synchronization.

Two MD1250 modules provide 2,500 kW of total capacity with full N+1 redundancy, making this configuration a direct competitor to the Caterpillar 3516B and Cummins QSK60 in the multi-megawatt data center and healthcare markets. The modular approach allows each module to be independently serviced without compromising facility backup power, and the smaller individual unit footprint simplifies rigging logistics compared to a single 2.5 MW genset.

The Mitsubishi S12R is EPA Tier 2 certified for stationary emergency applications. The engine features dual-circuit cooling (separate jacket water and aftercooler circuits) and a 158.5-quart oil capacity, requiring structured maintenance planning for multi-unit installations.

Our Service Experience#

The MD1250 shares the proven Mitsubishi S12R platform with the SD1250. The dual-circuit cooling system requires separate coolant sampling and maintenance for jacket water and aftercooler circuits on each module. At 97.7 gph per module at full load, fuel delivery infrastructure for multi-unit installations is a critical design consideration. We recommend oil analysis every 250 hours to track engine wear trends across the 12-cylinder valve train, and staggered major service intervals across modules to maintain continuous redundancy.

Engineering specifications

Physical

Length
215.7 in
Width
93 in
Height
115.1 in
Dry weight
26,045 lb

Fuel system & runtime

Fuel use @ full load
97.7 GPH
Fuel use @ 75% load
72.9 GPH
Fuel use @ 50% load
50.3 GPH

Thermal & ventilation

Heat to coolant
1,829,820 BTU/hr
Exhaust flow
12,570 CFM
Exhaust temp
932 °F
Combustion air
4,767 CFM
Ventilation air
66,100 CFM

Documents & downloads

Spec sheets & manuals

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

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Estimated runtime

2.7 hours(0.1 days)

Fuel consumption ≈ 75.37 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 Generac MD1250 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 500 hours
Fuel filter
Every 500 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 / degradationHard starting, filter clogging, reduced power output4,380+moderate
Paralleling controller synchronizationFailed sync, load sharing imbalance, hunting20,000+moderate
Coolant systemOverheating from coolant degradation in dual-circuit system4,000+moderate
TurbochargerReduced boost pressure, oil consumption from turbo seal wear12,000+severe
Starting batteriesFailure to crank the V12 from degraded batteries (4x12V system)2,000+moderate

Frequently Asked Questions

What is the difference between the MD1250 and the SD1250?
The MD1250 is a modular (factory-paralleled) system designed for scalable, redundant power architectures. It uses the same Mitsubishi S12R 49.0L V12 engine as the SD1250 but comes factory-configured with integrated paralleling controls, enabling plug-and-play expansion with additional MD units. The SD1250 is a single-unit standalone generator at the same power rating. The modular approach provides N+1 redundancy, easier installation logistics, and the ability to service one unit while another continues operating.
What is the fuel consumption of the MD1250?
The MD1250 uses the same Mitsubishi S12R engine as the SD1250. At standby rating, fuel consumption is approximately 97.7 gallons per hour at full load, 72.9 gph at 75% load, 50.3 gph at 50% load, and 30.0 gph at 25% load per module.
What voltages are available?
The MD1250 is available in three-phase configurations at 277/480V and 346/600V, both at 60 Hz.

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