Any question answered...

Heat to 92°C = 323.4 kJ = 0.0898 kWh = 1.52p @16.9p / kWh

Heat to 100°C = 357 kJ = 0.0992 kWh = 1.68p @16.9p / kWh

From UK Tea Assoc. https://www.tea.co.uk/tea-faqs

HOW MANY OF CUPS OF TEA DO THE BRITISH DRINK EACH DAY? A: Approximately 100 million cups daily, which is almost 36 billion per year [Source: ITC].

1 cup = 0.24 L
100 million cups = 24 million L = 24 mill kg H2O

Heat 24 million Kg to 92°C = 24 mill * 323.4 kJ = 7,761,600,000 kJ per day

Heat 24 million Kg to 100°C = 24 mill * 357 kJ = 8,568,000,000 kJ per day

Difference would be 806,400,000 kJ = 806.4 GJ saved every day by making tea slightly differently while minimally/not affecting the end product. (Someone review my working pls).