We all put too much water in our kettles every time we fill it. You only need to put in enough to a) cover the element and b) fill your cup(s) or whatever. Only 26% of people ever look at the water gauge.

When making coffee, the optimum water temperature is 85-90^oC, not 100^oC as it is out of a boiling kettle, which affects the taste.

Stove top kettles are less efficient than electric kettle, although using gas to heat the kettle has environmental benefits over electricity (unless of course you use green electricity).

Buy a kettle with a covered element – you can boil less water in them.

Descale the kettle regularly – especially if you live in a hard water area. Use vinegar as a descaler.

Think about the ethical reputation of the company you are buying the kettle from.

Gooshing has a wide range of kettles, including ethical ratings.

The Energy Saving Trust provide information on products and retailers.