Overview#
The 400 kW Kohler/Rehlko gaseous standby generator is sold as the 400REZXB — there is no Kohler model called "KG400." We've kept this URL because customers commonly search "Kohler KG400" when comparing 400 kW gas gensets, and we want them landing on accurate information.
The 400REZXB is the upper end of Kohler's industrial gaseous lineup: a Doosan/PSI 21.9L V12, turbocharged and aftercooled, producing 605 HP at 1800 RPM on natural gas or propane without a drop of diesel.
Above 400 kW gaseous, the answer is paralleling. Two 400REZXB units provide 800 kW with full N+1 redundancy; three provide 1.2 MW. This makes the 400REZXB a building block for large gaseous paralleling arrays at campuses, hospitals, and government facilities where air quality districts restrict diesel emissions.
The flagship platform#
- Turbocharged-aftercooled V12 — the aftercooler brings intake charge temperatures down for consistent power output in high-ambient conditions
- 12-cylinder V configuration — service envelope is large; access on both banks of the V12 is non-trivial
- Container or walk-in enclosure recommended for all installations
- Paralleling-ready — most 400REZXB installations are multi-unit arrays
When to use the 400REZXB#
- Paralleling arrays where gaseous is mandated (BAAQMD, other air districts)
- Single-unit maximum gaseous for sites that need 250-320 kW continuous (80% loading)
- Campus distribution where multiple smaller diesel units would create multiple SPCC plans
- Sites with reliable gas service and adequate supply pressure per the 400REZXB installation manual
Our service experience#
The 400REZXB is our largest gaseous service platform. Every unit we maintain is on a walk-in or container enclosure — there's no practical way to service a 21.9L V12 in a standard weather-protective cabinet. The aftercooler adds a service item (condensation drain, core inspection) that doesn't exist on the smaller naturally-aspirated or basic turbo units.
