15 minutes-1 hour or so. The time for cooking porridge in a small electric cooker mainly depends on the power of the electric cooker and the material for cooking porridge. Generally speaking, it takes about 15-20 minutes to cook common porridge such as millet porridge and rice porridge with a rice cooker. If it takes a long time to cook porridge, such as eight-treasure porridge, it will take longer, and it may take about 1 hour.