In most cases an inverter is a factory option. Sometimes it is only for the entertainment systems and is quite small, 300 watts or so. Some are meant to run the whole motor home as well as charge the batteries. These are usually 2000 watts with 100 amps of charging power. Batteries determine how long you can run the inverter. If you have only two group 24 batteries, you will be able to run your TV and satellite receiver for 4 or 5 hours. If you have a full house inverter, and the microwave runs on it, you should only use it for a few minutes. You can't run the air conditioning from an inverter. If your whole house is on the inverter, four six volt golf cart batteries would be best. If you have solar power you will be able recharge the batteries without plugging in. It will take a couple of hours of driving to recharge the batteries or several hours of being plugged in to shore power.