It really depends on what you are doing. For boiling water a simple immersion element is the most efficient, and gas the least efficient, with induction, resistive hotplate and microwave, in that order, in between.
Summary of some testing I did a few years ago:
Boiling water for a cuppa - which is the most efficient way?
Ever wondered which is the most energy efficient way to boil a cup of hot water?
I’ve done a comparison using several methods:
Induction cooktop with kettle +375ml water
Gas burner with same kettle +375ml water
Ceramic electric jug + 375ml water
Microwave oven with 375ml water in a large mug
Immersion heater in same large mug with 375ml water
Water temp was 12C
I don’t have any sort of electric hotplate, so that is not included in the comparison, however, it is considered to be less efficient than induction heating.
Results:
Immersion heater …118sec_____ 48.3Wh … @1473W
Electric jug …115sec_____ 51.6Wh …@ 1615W
Induction cooktop …101sec_____ 63Wh … @2246W
Microwave oven …171sec_____ 89.5Wh … @1884W
Gas burner …167sec_____ ~270Wh … @~5700W
EDIT: BTW, all tests done with off-grid solar power
