I wouldn't say an inverter is "necessary" but it's definitely "convenient." We have a factory 600w inverter and factory solar. We are able to watch TV in the evening for a couple of hours if we want and charge our laptops, phones, etc using the inverter without much impact on the batteries. The next day the battery is topped off by the solar. It's a nice combination. (I should point out that all our lighting has been converted to LED and we replaced the original Sony TV with a new Samsung flat screen, which is undoubtedly more energy-efficient ... so our usual "draw" on the batteries is much-reduced in general.) On a recent trip we went 5 days dry camping — even using the furnace lightly at night — without needing the generator and never going below 85% of battery power.
TB & Greg and Abbey Schnauzer
AirForums #21900 . Membership Chair, 4CUnit #3954
Travel Log: AZBambi...On the Road Again