The cheapest way is to plug your shore power cord into the inverter using a
$6 Adapter and turn off/disconnect the converter and microwave. The microwave draws a little current so I turn it off as well when using my 500W inverter. Have the fridge and water heater on propane if using them.
I also have a 100W inverter that plugs into the cigarette plug above the TV. That plug is only good for 8 amps. I use it for watching TV and charging our electronics. That's an isolated circuit so I don't need to worry about the converter.
