Our faithful electric kettle started to die about a week ago, the automatic cutoff kept cutting off long before the water in the kettle had reached boiling point. It was at least 10 years old and was otherwise in good working order.
We had a look online to see what to replace it with. It seems almost all modern kettles available in the UK are 1.7 l capacity and have a 3 kW electric heating element with a minimum water volume of 2 cups (unspecified actual volume). Our old kettle was a mere 2 kW and would happily boil as little as 300 ml (one decent mug full of water).
We don't have PV panels on the roof so wouldn't benefit from a 1 kW kettle but even so, 3 kW to boil more water than I need for a single mug of tea seems very silly and inefficient. There are a few eco kettles that manage to boil only one cup full of water but they are few and far between...
In the end we found a 2 kW unit with a 1 l capacity and low enough minimum water boil volume. But it cost twice what the larger version from the same manufacturer cost.
While I know that tea and coffee drinking is quite a social activity in the UK, but there are plenty of households with only one person in or who drinks hot beverages. It seems that most people are probably wasting quite a lot of energy on heating/re-heating water that they probably don't need to.