My experience with 12 volt appliances was the quality wasn't very good and they didn't last too long. The quality of mass produced 120 volt appliances that have to handle 1/10th the amps is much better.
The key to power efficiency of cooking is to get all the heat you create into the food. With hot plates the element has to heat up and then transfer that heat to the pan and then into the food. A lot of the heat radiates out the side. I use "cool touch" rice cookers to steam or boil meals. I took them apart and added a layer of foil internally to block more of the heat from escaping. The power losses of the inverter might be 15% but the heat losses of open appliances might be 50% so that is where the most power can be saved. I use an super insulated crock pot to can over 300 quarts of fruit each year. I took out the inner chamber and put 4 jars in. I had to remove the plastic parts and replace the cord with heat resistant wire. It uses less than 100 watt/hours to cook, sterilize, and seal each quart jar. I used to use it bake bread too. I now have a bread machine that uses 250 watt/hours for a loaf of bread
We also have an electric frying pan that we use less frequently. I'll usually throw a kitchen towel over it after the stirring is done to keep it hot until the rest of the meal is cooked. We do all of our cooking with electricity and have to juggle cookers to do multiple dishes with our 2000 watt inverter. The rule is to only use one large appliance at a time. So the frying pan needs to be unplugged if the microwave is needed to reheat something. If we had a larger 4000 watt inverter this wouldn't be such an issue.
So with my experience I'd start with some rice cookers off an inverter for emergency cooking or whenever you have enough surplus power.
Chris
