D.M. Procida wrote:

A leaflet that arrived with the electricity bill claims that our mobile
phone chargers will be sucking up 100kWh of electricity a day, whether
they are charging a phone or not.

What size battery would would suck up 100kWh a day? And who would I be
able to reach on the mobile phone?

Chargers do get warm if left plugged in but I find it hard to believe
this would amount to a tenth of a kilowatt in a day. Perhaps they have
selected the charger they are warning you about and it was an early
mobile phone charger circa 1980's.