Portable inverter generators hit the market around 2005 and have been growing in popularity ever since. They were created to address two of the main concerns associated with portable generators; they are loud and they are inefficient.
How Portable Inverter Generators Work
A normal portable generator puts our direct AC power from the motor. This means that the portable generator engine has to run at a minimum speed at all times to create the AC power. So no matter what the load you are putting on the generator is, it will always be running at a minimum number of RPMs (around 3,600) to create the AC power. This is where the inefficiencies lie. Inverter generators have solved this problem with a solution that is right there in the name; an inverter. DC power can be generated from an engine running much lower RPMs. Then the generator simply passes the DC power through an inverter and converts it to AC power.
With this simple method portable inverter generators are able to idle at a much lower RPM which reduces the noise they produce significantly. They also have a much more direct correlation between the RPMs and what the load requirements on the engine are which creates a much more efficient system.