What is the difference between an air-cooled and liquid-cooled generator

The engines! Air-cooled generators come with engines that use fans to force air across the engine for cooling, while liquid-cooled generators use enclosed radiator systems for cooling, similar to an automobile. Generally, liquid-cooled engines are used on larger kW generators due to the larger engines required for the higher power output. Liquid-cooled engines require less attention during power outages and have a longer life expectancy.