Electric Kettles are very heavy users of electricity and are frequently of 3kW power.   I have found that the traditional style kettle shape boils quicker, as there is more water exposed to the element than the popular Jug shape.   If I am brewing up just for myself, I just but a cupful of water in the kettle.   It is however, much cheaper to use a kettle on a gas stove, if you have one, than to use an electric kettle.