Of all the types of energy, it's easiest to turn other types of energy (such as electricity) into heat. That's why, when converting amongst other kinds of energy (such as light, or motion), a side effect is often heat (and things getting hot which don't need to be is a sign of an inefficient process).
Essentially the kettle just converts electricity to heat (very efficient) which heats the element inside the kettle which is transferred to the water surrounding it via conduction (also very efficient). There's almost no wasted energy, and you know that because the area around the kettle does not get hot.
Kettles do use a lot of energy because water requires a lot of energy to heat up - in fact it's among the highest of all substances (the measure of this is called the heat capacity or specific heat - the amount of energy to raise an amount of a substance by one degree Celcius/1 Kelvin.
If you want to be more energy efficient at boiling water, put only the amount of water you need in the kettle, rather than boiling extra, but obviously this is not a solution when scaling electricity infrastructure.
edit: I should note that Kettles are not completely efficient - there is still some energy loss (for instance, through resistance in the wiring in the kettle, and heat conducted to the kettle itself or radiated to the surrounding air).
Could one make a heat pump kettle that would be "more than 100% efficient", by moving head from the surrounding air into the water rather than just resistive heating? I remember seeing that approach recommended for heating houses.
Essentially the kettle just converts electricity to heat (very efficient) which heats the element inside the kettle which is transferred to the water surrounding it via conduction (also very efficient). There's almost no wasted energy, and you know that because the area around the kettle does not get hot.
Kettles do use a lot of energy because water requires a lot of energy to heat up - in fact it's among the highest of all substances (the measure of this is called the heat capacity or specific heat - the amount of energy to raise an amount of a substance by one degree Celcius/1 Kelvin.
If you want to be more energy efficient at boiling water, put only the amount of water you need in the kettle, rather than boiling extra, but obviously this is not a solution when scaling electricity infrastructure.
edit: I should note that Kettles are not completely efficient - there is still some energy loss (for instance, through resistance in the wiring in the kettle, and heat conducted to the kettle itself or radiated to the surrounding air).