Enter your kettle's power, roughly how many seconds it takes to boil and how often you boil it, and this works out the cost. Boiling only the water you need is the saving most people miss.
A kettle is high-powered but only runs for a couple of minutes, so each boil is cheap; the cost comes from how often, and how full, you boil it. Overfilling is the classic waste, since you pay to heat water you tip away. More in kettle energy saving.
Common questions
How much does it cost to boil a kettle?
A 3kW kettle boiling for about 150 seconds uses roughly 0.125 kWh, which at 26.11p costs around 3.3p a boil. Ten boils a day is about £12 a year.
Does boiling less water save money?
Yes. The cost is set by how much water you heat, so filling the kettle to just what you need, rather than to the top, cuts both the boiling time and the cost every single time.