Converter charges batteries, must be on
Stand alone inverter uses batteries to make 120vac power, can be turned off if not using it
Combo inverter-chargers do both functions
The charge function needs to be on all the time
The 'inverter' function can be turned off, if you wish
Although mine was always on
If you have cable TV satellite TV or cable internet, leave the inverter function ON
Or everything is going to turn off and reset every time the shore power blips