Originally Posted by twinboat
Inverter generators vary the engine speed based on load. Most time they are not running full speed.
The inverter section is also more compact so they can pack it in a smaller insulated case to keep the noise down.
A standard contractor generator runs at 3600 RPM for 60 cycle power. Basicly a noisey utility engine.
A slower turning engine ( 1800 or 2700 RPM ), although quieter, needs a bit more power to turn the same alternator at 3600 RPM thru belts and pullies. That's how most gas RV generators work.
Direct drive slow speed generators ( diesel ) need double the poles to create 60 cycles at that speed. That costs more money.
The 6.3KW propane powered Onan generator in my coach runs at a constant 1800 RPM, has no belt or pulleys, and is relatively quiet.