Microwave was best upgrade to cabin
This isn't 12 volts but, I tossed out the factory alchohol stove and found a small 750 watt microwave that fit the space. I use a 2500watt inverter powered by two 100 amp rv batteries. I kept a daily log of microwave use and the results are that the microwave ran for 56 minutes (intermitent use)before he inverter low voltage alarm went off. This was a weeks cruising two years ago. Now I keep the batteries topped up with a small solar panel and the outboard. The alarm has never gone off again.
Next to fixing window and deck leaks, the microwave is my best upgrade.
I know if you extensively cruised or cooked a turkey everyday it would not work for you but 56 minutes is a lot of microwave time for hotdogs and popcorn.