Originally Posted by mitiempo
If a microwave is used sparingly, as they nearly always are, the DC amp usage is pretty low. An inverter is needed. But your 1200 watt example need not be that high. A small microwave at 700 watts AC will use about 70 amps DC through the inverter. 5 minutes of use to heat something up or make popcorn or whatever will use 70 divided by 12 or a bit less than 6 amps DC.
I have a 700 watt microwave on my 27' boat.
I think that the 700W figure is the power delivered by the oven, not the current draw. It may not require 1200W, but I would be surprised if it wasn't pretty close to 1kW. While it's true that a few minutes here and there wouldn't tax most house banks too much, it would still be a fairly large percentage of a daily electrical energy usage. At the dock, no biggie. While cruising,....? Of course, there is always the space issue. A second appliance for doing what can be done by the stove isn't usually what a small boat really needs. However, for a live aboard things might be a bit different.