Inverters are designed to allow you to operate appliances from your 12V battery system without shore power or your generator.
Inverters are not chargers.
Some inverters will have a built in charger to help compensate for what the inverter will draw out of the battery(s) when operating an appliance.
An inverter can be handy when you want that pot of coffee and it is before or after generator hours and/or you don’t have a generator.
Keep in mind what you take out the battery has to be put back. An investment in a good charging system makes sense if you want to use a large inverter.
The first is to operate TV’s, satellite dishes, and laptop computers or similar products. A 500 or 600 watt inverter is great and inexpensive for these tasks.
The next step up is for those customers who want to use a microwave, coffeepot or other larger power hungry device. A 1500 to 2500 watt inverter will work for these. Remember a larger bank of batteries will allow you to last longer but still what you take out needs to be put back.