Again the discussion being resistive versus microwave, restive should be better even in an instant water heater, again microwave has no advantage that I see. A

Again the discussion being resistive versus microwave, restive should be better even in an instant water heater, again microwave has no advantage that I see. And when talking about efficiency you must specify context. In this case heating water via electricity, not losses of storing the heated water which is a separate issue based on tank vs instant regardless of heating method.