These kettles from Eco Kettle are Energy Saving Trust recommended and work in two main energy saving ways.
The basic Eco Kettle 2 (Chrome or White) has a store that is filled up and then released into the boiling chamber by a simple push knob system. This allows you to fill up the kettle and then just boil as much water as you need on an individual basis during the day.
The more advanced Eco Kettle 3 (Chrome only) has some clearer electronics that allow you to heat the water up to different temperatures that are ideal for difference purposes:
100 degrees for tea
90 degrees for coffee (a simple and automatic way of not scolding the grounds)
80 degrees for herbal infusions etc.
The Eco Kettle 3 is therefore a really excellent energy saving device for people who enjoy a range of drinks during the day.