Sir, Greg Leonard's letter (6 September) would save electricity but soon put scales on the uncovered section of his kettle's electric element. The correct solution is to fill the kettle so as to cover the element, use the amount required for tea, and put the rest into a vacuum flask for washing up the tea things.
Another answer is a simple solar cooker. Shaped like a satellite dish, and turned towards the sun at half-hour intervals, this boils three pints of cold water in a blackened kettle in an hour or two at no expense or addition to global warming.
West Wittering, West Sussex