Generac · MG Series (Modular Gaseous)

Generac MG625

625 kW standby · Natural Gas / LPG · Liquid-cooled

625 kW modular natural gas standby generator system. Factory-paralleled for N+1 redundancy.

Standby power
625 kW
Voltage options
120/208V, 120/240V, 277/480V, 346/600V
Frequency / Phase
60 Hz · 3-phase
Engine
Generac 33.9L V12 SI · 33.9L
Alternator
Generac K0732124Y22
CommercialManufacturingHealthcareData CentersGovernment
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Overview#

The Generac MG625 is a 625 kW modular natural gas generator rated at 625 kW / 781 kVA standby at 60 Hz. It uses a Generac turbocharged/aftercooled 33.9L V12 spark-ignited engine with a 126.8-quart oil capacity and 55-gallon coolant system. Built on the Modular Power System (MPS) platform with a Power Zone Pro Sync controller, the MG625 enables N+1 redundancy configurations for mission-critical facilities. The 4-valve cylinder head design provides efficient combustion at this power class.

Our Service Experience#

The MG625 uses the Generac 33.9L V12 turbocharged/aftercooled engine at 625 kW (226 psi BMEP per the spec sheet). Exhaust temperatures reach 1,166 F post-catalyst at rated output. With 12 spark plugs per unit and a 126.8-quart crankcase (approximately 32 gallons of oil per change), service events are substantial. The fuel demand of 6,847 CFH at full load requires dedicated gas supply infrastructure with proper regulator sizing (14-20 in H2O operating pressure). The 55-gallon coolant system uses 50/50 ethylene glycol antifreeze.

Engineering specifications

Physical

Length
178.3 in
Width
82.6 in
Height
110.3 in
Dry weight
14,352 lb

Documents & downloads

Spec sheets & manuals

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Estimate runtime for the Generac MG625

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

Estimate runtime on this tank

Fuel demand at 75% load

6,562,500 BTU/hr≈ 6562.5 cf/min @ 1,000 BTU/cf

On utility natural gas the runtime is generally unlimited provided the supply line and meter can deliver this BTU/hr at the engine's required inlet pressure (typically 5–14" WC residential, up to 5 psi commercial). Confirm against the OEM's published fuel-pressure spec.

Service intervals

Manufacturer-recommended intervals for the Generac MG625 under standby duty. Field intervals may differ based on load profile, ambient conditions, and fuel quality.

Oil & filter
Every 500 hours or 12 months
Air filter
Every 1000 hours
Spark plugs
Every 2000 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
Spark plugsMisfiring, rough running, reduced power output2,000+minor
Gas regulator / fuel trainUnstable speed, hard starting, fuel pressure faults15,000+moderate
Paralleling controller synchronizationFailed sync, load sharing imbalance, hunting20,000+moderate
BatteryFailed to start, slow cranking8,760+minor

Frequently Asked Questions

What is the difference between the MG625 and the SG625?
The MG625 is a 625 kW gaseous generator built on Generac's Modular Power System (MPS) platform using a turbocharged/aftercooled 33.9L V12 engine with factory-integrated paralleling capability. The SG625 uses the same 33.9L V12 engine platform but is configured as a standalone unit. The MG625's MPS architecture enables N+1 redundancy configurations and the ability to service one unit while others continue operating.
What fuel types does the MG625 support?
The MG625 supports both natural gas and liquid propane (LP/LPG). Natural gas is the most common fuel choice as it eliminates fuel storage requirements and provides unlimited runtime with utility gas service.
What voltages are available?
The MG625 supports three-phase configurations: 120/208V, 120/240V, 277/480V, and 346/600V at 60 Hz.

Compatible equipment

Transfer switches

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