There's a British phenomenon called a 'TV Pickup,' huge surges of people using appliances during commercials
People in Britain tend to watch the same TV shows at the same time. This means that millions of people are not only watching the same show, they're also getting commercial breaks at the same time. When a show you're watching goes to commercial, you might get up and go get a soda for the fridge, or turn on your teakettle and boil some water. Now imagine millions of people doing that at the exact same time.
The British National Grid actually spends a lot of time predicting these TV Pickups because of the extra strain they can put on the electric service. A miscalculation could mean power loss for many people. The average pickup is an extra demand for between 200 to 400 MW. The most popular time for the pickups is at 9PM.
The larger the event or TV show, the larger the surge. The biggest one in history was recorded in 1990, when there was a penalty shootout between England and West Germany in the FIFA World Cup semi-final. Royal weddings and soaps are other shows that cause huge surges.
Although it's still a big problem for the National Grid, the increasing number of cable TV channels is reducing the number of TV Pickups. Nevertheless, it's still a huge pain for them because of all that they have to scramble to meet demand.