Generator Ventilation Calculator
Calculate the required cooling airflow (CFM) and louver sizes for generator sheds, rooms, and enclosures to prevent overheating.
Installation Parameters
Portable & small standby units. Heat radiates directly from engine.
Required Airflow
Total Heat Rejected
-- BTU/min
Est. Combustion Air
-- CFM
Recommended Louver Sizes (Free Area)
*Values are Net Free Area. Total frame size must be larger (typically 1.5x - 2x) depending on blade obstruction.
Understanding Generator Cooling
Generators produce massive amounts of heat. Only about 20-35% of the fuel energy becomes electricity; the rest becomes heat that must be removed to prevent engine failure.
Sizing Rules of Thumb
Air Cooled Units
Typically 20kW or smaller. The engine radiates heat directly into the room.
Formula: CFM = H / (1.08 × ΔT)
H ≈ (KW × 3412) × 1.5 (Radiated Heat Factor)
Liquid Cooled Units
Larger units with radiators. Most heat is removed by the radiator fan, but engine surface heat still warms the room.
Radiated Heat Factor ≈ 0.4 - 0.6
*Note: Radiator fan CFM is usually sufficient if ducted out correctly.
Combustion Air
In addition to cooling air, the engine needs air to burn fuel. This is typically estimated at 2.5 CFM per kW rated output. This calculator adds combustion air to the total cooling requirement.