I'll wade into this... If you are running anything with a fan/motor, you want a pure sine wave inverter. That means nice curvy waveforms, vs the alternative, which is basically square waves that motors don't like. For that matter, sensitive electronics don't like square waves, nor does radio gear.
Sine wave inverters cost a lot more, and you have to decide what you want to do. Just charge batteries on your electronics/camera/phone? A small 300W square wave will do, and these normally plug into your cigaretter lighter. I chopped the plug off of mine and wired it into the battery comparment and an ac outlet - done.
If you want to run something bigger like a big'ish screen or CPAP machine or - toaster oven - you will need that 2000W unit, and the batteries to run it.
Something to think about. A 1500W toaster oven is drawing 1500/120 = 12.5A in your house. Assuming 80% efficiency at converting the 12v DC in your batteries to 120v AC that the toaster needs, you need to deliver 156A to the inverter.
The wires had better be beefy, and short, and your batteries big if you want to cook much of anything!
FYI, I looked at my friends CPAP machine and it was rated at 80 watts. Newer generation unit.
Edited by Ronski, 16 January 2018 - 08:31 PM.