Many houses built in the last century were built with minimal electrical service. When looking back to those times, there simply weren't that many electrical devices in a home. AC was not available until after World War II, and in 1955 only 10 percent of US households have electric clothes dryers. You can explore more information about electrical services in Christchurch via https://insightelectrical.co.nz/.
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Hairdryer, toaster oven, electric range, microwave, electric water heaters, and other things like that added over the years, greatly increasing electricity demands.
However, when the homeowner with basic services such as start adding modern equipment, they quickly run out of electricity capacity, which could lead to the dissolution of the local circuit breaker or fuse is blown, or cable overheating and possible fire hazard.
Computers did not take much, but they do not like brownouts or movies in power. For any type of computer or computerized equipment, it's a good idea to use surge suppressors and uninterruptible power supplies to prevent damage. This includes computerized sewing machines, sports equipment, TV, digital video recorder and cable box.
Another consideration when the old houses are that many of the wires coming from the pole to the house, and then down the house to meter, aged 40-50 years and is now in tatters. Often the wire wrapped around the center conductor is now showing through.