Why add a new Inverter when adding Solar to your RV?

Do you mean converter? No you might even just switch it off.

You need an inverter if you want to have some 120vac power to charge small items like phones and laptops or run a tv.
Upgrade is usually to run bigger stuff like microwave, hair drier etc but then you are in 2000w and four batteries.

Here are some threads on solar:

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