Sizing Inverter Help
If you have an all DC voltage system (using all DC lights and appliances) you don't need an inverter. If you are planning to use AC (house current) appliances you will need an inverter that is large enough to power all of the lights and appliances that you will have on at one time. If you use two or three or more large usage appliances at once you will need a larger inverter. If you can plan on using them at different times you can use a smaller inverter.
Example: You plan on using a toaster which uses 1100 watts and a microwave which uses 800 watts at the same time. You will need at least a 2400 watt inverter. If you use them at different times and are only using a few lights and maybe a TV at the same time, you can use a 1500 watt inverter or maybe a 1300 watt inverter.
For systems tied to the utility grid pick the 4000 watt inverter as it is the only one listed that produces power that satisfies normal utility specifications.