While the maximum energy efficiency for cooking is obtained with modern equipment, like microwave ovens, cooking equipment does not necessarily have to be modern and expensive.
I am pretty certain that the kitchen stove used by my grandparents had a much better energy efficiency than the kitchen stoves that burn natural gas and which are still very widespread now.
That old kitchen stove was a wood-burning kitchen stove, but only a small quantity of wood had to be burned, because it had a huge thermal inertia and after becoming hot enough food could be cooked for hours with minimal wood consumption. The heat transfer from the large hot iron stove (but with a temperature close to that needed for food, i.e. much lower than the temperature of a gas flame) was much better than from a gas burner, which resulted in much less lost heat.
The efficiency of such a wood-burning kitchen stove is likely to have been similar with the efficiency of an induction electric stove.
