Hi #10 wire would do for about 300 watts (I.E. ~24 amps @ 12.8 volts)
My drip coffee maker draws a little over 400 watts and consumes about 7 amp-hours of power to make a four cup pot.
The limiting factor may be the size of the battery bank. Type of battery may be a consideration as is the voltage of each jar.
AGM's are probably the best conventional battery to use. LI are still pretty pricey and can't be recharged in low temperatures -20 C(-4 F).
I tend to run my RV 100% electrically even when I have no shore power.