Idle current All inverters use some power even when no loads are turned on. This is the idle current of the inverter. It is a fixed amount and is always present as a load on your battery when your inverter is turned on. Some inverters have a search mode which reduces idle current by turning the inverter on and off every second to search for a load. If no load is present the inverter stays in search mode.
Many inverters feature built in battery chargers.
This allows the battery to be charged from an AC power source such as a generator or the utility. When an inverter is used in a back up power system the battery charger is a key feature of the inverter. If a significant amount of the power being delivered to your battery is coming from a generator, battery charger size may be very important. Having a charger that is too small will require running your generator for too long under a low load to achieve a proper charge. It is most efficient to use your generator to its maximum capacity so you can minimize the running time.