You don't likely 'need' an inverter. RVers have them for when they need to use items that require AC power, when they're not connected to shore power or generator power.
That said, you need a battery or battery bank to power the inverter from. Then you ultimately will need to recharge the batteries.
Does this help? If not, keep asking questions and I or others will jump in here to do our best to answer them for you.