The Victron MultiPlus inverter charger can sync with a small generator to provide additional power to start a load like an air conditioner that the generator by itself wouldn't be able to get started. The example below is a screenshot from the Color Control GX which is the system monitor.

MultiPlus in power assist mode

In the picture above the load is consuming 3510 Watts, 3129 Watts are coming from the generator, and the MultiPlus is making up the difference.  The behavior of the MultiPlus is programmable and in the screenshot below which is from the VE Configure program used to set up the MultiPlus you can see how the Boost Factor is set.

Boost Factor