Really sorry to hear about you losing your home in Jamul - nice area - and I hope your health is better too. Microwaves do have power spikes - sometimes more than others depending on what's being cooked, but even when they don't spike, they still consume a lot of power just running. The inverter has to be able to provide power at all times or it will overload and shut down. I'm sorry to say that I don't know how much power smaller microwaves consume. Without knowing that, I'm hesitant to recommend an inverter size, but I'd be willing to bet that a 1500 watt inverter - properly wired to a 300 to 400 amp hour battery-bank, would be able to power a small microwave for short periods of time. Maybe someone here who has such a setup, and who knows, will chime in.
Factory installed inverters are usually in the 1000 to 2000 watt range. Ours is 2800 watts - largely because we have a large res-fridge. You can install aftermarket inverters of all sizes, but installing one with higher-than-needed wattage is pointless. Inverters themselves consume power and are not 100% efficient (Ours is rated at 85% efficient.)The higher the wattage, the more power they consume.
We have an 840 AH battery-bank, and while it has no problem powering the inverter and microwave, the lights do dim when the microwave surges. I don't think I'd run the microwave unless my batteries were at 80% or better. It just draws to much power. If/when you install an inverter, place it as close to the battery-bank as possible (but not in the same compartment.) and use 4 AWG wire or better.
Kev
