This title may count as hyperbole, but like many simple things it bears a little thought.
I noticed that my kettle tends to 'over-boil' the water, i.e. it doesn't shut off until some time after the water in the kettle is clearly boiling. This is a common behaviour of kettles, in my experience. So I wondered how much energy this was wasting.
The kettle concerned is a 3kW kettle. I normally boil about 500ml of water ( about a couple of mugs worth ). This kettle takes at least 10s to shut off after the water reaches boiling point. I boil the kettle about 5 times a day.
Therefore I'm wasting 50s of power at 3kW every day. This is 50/3600 * 3000 Watt hours. This turns out to be about 42 Watt hours. If I repeat this pattern every day of the year, that's 15120 Watt hours, or about 15kW hours. If 20% of the population of the UK ( a figure plucked from the air ) follow the same pattern, that's 198,000,000kW hours, or 198 Gigawatt hours per year. A large power station generates about 5 Gigawatts, which is 43800 Gigawatt hours per year. So the overboiling kettles are using about 0.5% of one power station.
Many caveats could be applied to this calculation. Not all kettles are 3kW, not all will overboil by as much, maybe only 10% of the population drink this amount of hot beverage, but this is not an attempt at measurement but order of magnitude estimation.
On the one hand, this amount of power is in the noise margin - avoiding overboiling by mandating the redesign of kettles would have a negligible impact on the nation's power consumption.
On the other hand, 198 Gigawatt hours is not an insignificant amount of power - an average UK home consumes 3700kW hours per year, so this amount of power would suffice for 53500 households, or a substantial town.
The upshot of this consideration is therefore ambiguous, and falls into the category of 'absolute vs relative' disputes that have no simple resolution.
Personally, the idea that we're wasting something on the order of 198 Gigawatt hours on cups of tea and coffee ( ok, maybe Ovaltine too... ) simply because of a technical deficiency in kettles seems horrendous, when solving the problem is simply a matter of selling slightly smarter kettles. There is no technical challenge - such kettles already exist. I know because I bought one. It cost me twice what a 'dumb' kettle would cost, but when the water hits 100 degrees C it stops. And it only cost me twice as much because manufacturers are allowed to sell dumb kettles.
The lifespan of a kettle is order of 10 years, so change cannot happen fast, but IMHO your next kettle should know when it's done.
© Mark de Roussier 2021, all rights reserved.